diff --git a/pkg/relabel/relabel.go b/pkg/relabel/relabel.go
new file mode 100644
index 0000000000..775051474c
--- /dev/null
+++ b/pkg/relabel/relabel.go
@@ -0,0 +1,115 @@
+// Copyright 2015 The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package relabel
+
+import (
+	"crypto/md5"
+	"fmt"
+	"strings"
+
+	"github.com/prometheus/common/model"
+
+	"github.com/prometheus/prometheus/config"
+	"github.com/prometheus/prometheus/pkg/labels"
+)
+
+// Process returns a relabeled copy of the given label set. The relabel configurations
+// are applied in order of input.
+// If a label set is dropped, nil is returned.
+// May return the input labelSet modified.
+func Process(labels labels.Labels, cfgs ...*config.RelabelConfig) labels.Labels {
+	for _, cfg := range cfgs {
+		labels = relabel(labels, cfg)
+		if labels == nil {
+			return nil
+		}
+	}
+	return labels
+}
+
+func relabel(lset labels.Labels, cfg *config.RelabelConfig) labels.Labels {
+	values := make([]string, 0, len(cfg.SourceLabels))
+	for _, ln := range cfg.SourceLabels {
+		values = append(values, lset.Get(string(ln)))
+	}
+	val := strings.Join(values, cfg.Separator)
+
+	lb := labels.NewBuilder(lset)
+
+	switch cfg.Action {
+	case config.RelabelDrop:
+		if cfg.Regex.MatchString(val) {
+			return nil
+		}
+	case config.RelabelKeep:
+		if !cfg.Regex.MatchString(val) {
+			return nil
+		}
+	case config.RelabelReplace:
+		indexes := cfg.Regex.FindStringSubmatchIndex(val)
+		// If there is no match no replacement must take place.
+		if indexes == nil {
+			break
+		}
+		target := model.LabelName(cfg.Regex.ExpandString([]byte{}, cfg.TargetLabel, val, indexes))
+		if !target.IsValid() {
+			lb.Del(cfg.TargetLabel)
+			break
+		}
+		res := cfg.Regex.ExpandString([]byte{}, cfg.Replacement, val, indexes)
+		if len(res) == 0 {
+			lb.Del(cfg.TargetLabel)
+			break
+		}
+		lb.Set(string(target), string(res))
+	case config.RelabelHashMod:
+		mod := sum64(md5.Sum([]byte(val))) % cfg.Modulus
+		lb.Set(cfg.TargetLabel, fmt.Sprintf("%d", mod))
+	case config.RelabelLabelMap:
+		for _, l := range lset {
+			if cfg.Regex.MatchString(l.Name) {
+				res := cfg.Regex.ReplaceAllString(l.Name, cfg.Replacement)
+				lb.Set(res, l.Value)
+			}
+		}
+	case config.RelabelLabelDrop:
+		for _, l := range lset {
+			if cfg.Regex.MatchString(l.Name) {
+				lb.Del(l.Name)
+			}
+		}
+	case config.RelabelLabelKeep:
+		for _, l := range lset {
+			if !cfg.Regex.MatchString(l.Name) {
+				lb.Del(l.Name)
+			}
+		}
+	default:
+		panic(fmt.Errorf("retrieval.relabel: unknown relabel action type %q", cfg.Action))
+	}
+
+	return lb.Labels()
+}
+
+// sum64 sums the md5 hash to an uint64.
+func sum64(hash [md5.Size]byte) uint64 {
+	var s uint64
+
+	for i, b := range hash {
+		shift := uint64((md5.Size - i - 1) * 8)
+
+		s |= uint64(b) << shift
+	}
+	return s
+}
diff --git a/pkg/relabel/relabel_test.go b/pkg/relabel/relabel_test.go
new file mode 100644
index 0000000000..64c3fe5484
--- /dev/null
+++ b/pkg/relabel/relabel_test.go
@@ -0,0 +1,423 @@
+// Copyright 2015 The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package relabel
+
+import (
+	"reflect"
+	"testing"
+
+	"github.com/prometheus/common/model"
+
+	"github.com/prometheus/prometheus/config"
+	"github.com/prometheus/prometheus/pkg/labels"
+)
+
+func TestRelabel(t *testing.T) {
+	tests := []struct {
+		input   labels.Labels
+		relabel []*config.RelabelConfig
+		output  labels.Labels
+	}{
+		{
+			input: labels.FromMap(map[string]string{
+				"a": "foo",
+				"b": "bar",
+				"c": "baz",
+			}),
+			relabel: []*config.RelabelConfig{
+				{
+					SourceLabels: model.LabelNames{"a"},
+					Regex:        config.MustNewRegexp("f(.*)"),
+					TargetLabel:  "d",
+					Separator:    ";",
+					Replacement:  "ch${1}-ch${1}",
+					Action:       config.RelabelReplace,
+				},
+			},
+			output: labels.FromMap(map[string]string{
+				"a": "foo",
+				"b": "bar",
+				"c": "baz",
+				"d": "choo-choo",
+			}),
+		},
+		{
+			input: labels.FromMap(map[string]string{
+				"a": "foo",
+				"b": "bar",
+				"c": "baz",
+			}),
+			relabel: []*config.RelabelConfig{
+				{
+					SourceLabels: model.LabelNames{"a", "b"},
+					Regex:        config.MustNewRegexp("f(.*);(.*)r"),
+					TargetLabel:  "a",
+					Separator:    ";",
+					Replacement:  "b${1}${2}m", // boobam
+					Action:       config.RelabelReplace,
+				},
+				{
+					SourceLabels: model.LabelNames{"c", "a"},
+					Regex:        config.MustNewRegexp("(b).*b(.*)ba(.*)"),
+					TargetLabel:  "d",
+					Separator:    ";",
+					Replacement:  "$1$2$2$3",
+					Action:       config.RelabelReplace,
+				},
+			},
+			output: labels.FromMap(map[string]string{
+				"a": "boobam",
+				"b": "bar",
+				"c": "baz",
+				"d": "boooom",
+			}),
+		},
+		{
+			input: labels.FromMap(map[string]string{
+				"a": "foo",
+			}),
+			relabel: []*config.RelabelConfig{
+				{
+					SourceLabels: model.LabelNames{"a"},
+					Regex:        config.MustNewRegexp(".*o.*"),
+					Action:       config.RelabelDrop,
+				}, {
+					SourceLabels: model.LabelNames{"a"},
+					Regex:        config.MustNewRegexp("f(.*)"),
+					TargetLabel:  "d",
+					Separator:    ";",
+					Replacement:  "ch$1-ch$1",
+					Action:       config.RelabelReplace,
+				},
+			},
+			output: nil,
+		},
+		{
+			input: labels.FromMap(map[string]string{
+				"a": "foo",
+				"b": "bar",
+			}),
+			relabel: []*config.RelabelConfig{
+				{
+					SourceLabels: model.LabelNames{"a"},
+					Regex:        config.MustNewRegexp(".*o.*"),
+					Action:       config.RelabelDrop,
+				},
+			},
+			output: nil,
+		},
+		{
+			input: labels.FromMap(map[string]string{
+				"a": "abc",
+			}),
+			relabel: []*config.RelabelConfig{
+				{
+					SourceLabels: model.LabelNames{"a"},
+					Regex:        config.MustNewRegexp(".*(b).*"),
+					TargetLabel:  "d",
+					Separator:    ";",
+					Replacement:  "$1",
+					Action:       config.RelabelReplace,
+				},
+			},
+			output: labels.FromMap(map[string]string{
+				"a": "abc",
+				"d": "b",
+			}),
+		},
+		{
+			input: labels.FromMap(map[string]string{
+				"a": "foo",
+			}),
+			relabel: []*config.RelabelConfig{
+				{
+					SourceLabels: model.LabelNames{"a"},
+					Regex:        config.MustNewRegexp("no-match"),
+					Action:       config.RelabelDrop,
+				},
+			},
+			output: labels.FromMap(map[string]string{
+				"a": "foo",
+			}),
+		},
+		{
+			input: labels.FromMap(map[string]string{
+				"a": "foo",
+			}),
+			relabel: []*config.RelabelConfig{
+				{
+					SourceLabels: model.LabelNames{"a"},
+					Regex:        config.MustNewRegexp("f|o"),
+					Action:       config.RelabelDrop,
+				},
+			},
+			output: labels.FromMap(map[string]string{
+				"a": "foo",
+			}),
+		},
+		{
+			input: labels.FromMap(map[string]string{
+				"a": "foo",
+			}),
+			relabel: []*config.RelabelConfig{
+				{
+					SourceLabels: model.LabelNames{"a"},
+					Regex:        config.MustNewRegexp("no-match"),
+					Action:       config.RelabelKeep,
+				},
+			},
+			output: nil,
+		},
+		{
+			input: labels.FromMap(map[string]string{
+				"a": "foo",
+			}),
+			relabel: []*config.RelabelConfig{
+				{
+					SourceLabels: model.LabelNames{"a"},
+					Regex:        config.MustNewRegexp("f.*"),
+					Action:       config.RelabelKeep,
+				},
+			},
+			output: labels.FromMap(map[string]string{
+				"a": "foo",
+			}),
+		},
+		{
+			// No replacement must be applied if there is no match.
+			input: labels.FromMap(map[string]string{
+				"a": "boo",
+			}),
+			relabel: []*config.RelabelConfig{
+				{
+					SourceLabels: model.LabelNames{"a"},
+					Regex:        config.MustNewRegexp("f"),
+					TargetLabel:  "b",
+					Replacement:  "bar",
+					Action:       config.RelabelReplace,
+				},
+			},
+			output: labels.FromMap(map[string]string{
+				"a": "boo",
+			}),
+		},
+		{
+			input: labels.FromMap(map[string]string{
+				"a": "foo",
+				"b": "bar",
+				"c": "baz",
+			}),
+			relabel: []*config.RelabelConfig{
+				{
+					SourceLabels: model.LabelNames{"c"},
+					TargetLabel:  "d",
+					Separator:    ";",
+					Action:       config.RelabelHashMod,
+					Modulus:      1000,
+				},
+			},
+			output: labels.FromMap(map[string]string{
+				"a": "foo",
+				"b": "bar",
+				"c": "baz",
+				"d": "976",
+			}),
+		},
+		{
+			input: labels.FromMap(map[string]string{
+				"a":  "foo",
+				"b1": "bar",
+				"b2": "baz",
+			}),
+			relabel: []*config.RelabelConfig{
+				{
+					Regex:       config.MustNewRegexp("(b.*)"),
+					Replacement: "bar_${1}",
+					Action:      config.RelabelLabelMap,
+				},
+			},
+			output: labels.FromMap(map[string]string{
+				"a":      "foo",
+				"b1":     "bar",
+				"b2":     "baz",
+				"bar_b1": "bar",
+				"bar_b2": "baz",
+			}),
+		},
+		{
+			input: labels.FromMap(map[string]string{
+				"a":             "foo",
+				"__meta_my_bar": "aaa",
+				"__meta_my_baz": "bbb",
+				"__meta_other":  "ccc",
+			}),
+			relabel: []*config.RelabelConfig{
+				{
+					Regex:       config.MustNewRegexp("__meta_(my.*)"),
+					Replacement: "${1}",
+					Action:      config.RelabelLabelMap,
+				},
+			},
+			output: labels.FromMap(map[string]string{
+				"a":             "foo",
+				"__meta_my_bar": "aaa",
+				"__meta_my_baz": "bbb",
+				"__meta_other":  "ccc",
+				"my_bar":        "aaa",
+				"my_baz":        "bbb",
+			}),
+		},
+		{ // valid case
+			input: labels.FromMap(map[string]string{
+				"a": "some-name-value",
+			}),
+			relabel: []*config.RelabelConfig{
+				{
+					SourceLabels: model.LabelNames{"a"},
+					Regex:        config.MustNewRegexp("some-([^-]+)-([^,]+)"),
+					Action:       config.RelabelReplace,
+					Replacement:  "${2}",
+					TargetLabel:  "${1}",
+				},
+			},
+			output: labels.FromMap(map[string]string{
+				"a":    "some-name-value",
+				"name": "value",
+			}),
+		},
+		{ // invalid replacement ""
+			input: labels.FromMap(map[string]string{
+				"a": "some-name-value",
+			}),
+			relabel: []*config.RelabelConfig{
+				{
+					SourceLabels: model.LabelNames{"a"},
+					Regex:        config.MustNewRegexp("some-([^-]+)-([^,]+)"),
+					Action:       config.RelabelReplace,
+					Replacement:  "${3}",
+					TargetLabel:  "${1}",
+				},
+			},
+			output: labels.FromMap(map[string]string{
+				"a": "some-name-value",
+			}),
+		},
+		{ // invalid target_labels
+			input: labels.FromMap(map[string]string{
+				"a": "some-name-value",
+			}),
+			relabel: []*config.RelabelConfig{
+				{
+					SourceLabels: model.LabelNames{"a"},
+					Regex:        config.MustNewRegexp("some-([^-]+)-([^,]+)"),
+					Action:       config.RelabelReplace,
+					Replacement:  "${1}",
+					TargetLabel:  "${3}",
+				},
+				{
+					SourceLabels: model.LabelNames{"a"},
+					Regex:        config.MustNewRegexp("some-([^-]+)-([^,]+)"),
+					Action:       config.RelabelReplace,
+					Replacement:  "${1}",
+					TargetLabel:  "0${3}",
+				},
+				{
+					SourceLabels: model.LabelNames{"a"},
+					Regex:        config.MustNewRegexp("some-([^-]+)-([^,]+)"),
+					Action:       config.RelabelReplace,
+					Replacement:  "${1}",
+					TargetLabel:  "-${3}",
+				},
+			},
+			output: labels.FromMap(map[string]string{
+				"a": "some-name-value",
+			}),
+		},
+		{ // more complex real-life like usecase
+			input: labels.FromMap(map[string]string{
+				"__meta_sd_tags": "path:/secret,job:some-job,label:foo=bar",
+			}),
+			relabel: []*config.RelabelConfig{
+				{
+					SourceLabels: model.LabelNames{"__meta_sd_tags"},
+					Regex:        config.MustNewRegexp("(?:.+,|^)path:(/[^,]+).*"),
+					Action:       config.RelabelReplace,
+					Replacement:  "${1}",
+					TargetLabel:  "__metrics_path__",
+				},
+				{
+					SourceLabels: model.LabelNames{"__meta_sd_tags"},
+					Regex:        config.MustNewRegexp("(?:.+,|^)job:([^,]+).*"),
+					Action:       config.RelabelReplace,
+					Replacement:  "${1}",
+					TargetLabel:  "job",
+				},
+				{
+					SourceLabels: model.LabelNames{"__meta_sd_tags"},
+					Regex:        config.MustNewRegexp("(?:.+,|^)label:([^=]+)=([^,]+).*"),
+					Action:       config.RelabelReplace,
+					Replacement:  "${2}",
+					TargetLabel:  "${1}",
+				},
+			},
+			output: labels.FromMap(map[string]string{
+				"__meta_sd_tags":   "path:/secret,job:some-job,label:foo=bar",
+				"__metrics_path__": "/secret",
+				"job":              "some-job",
+				"foo":              "bar",
+			}),
+		},
+		{
+			input: labels.FromMap(map[string]string{
+				"a":  "foo",
+				"b1": "bar",
+				"b2": "baz",
+			}),
+			relabel: []*config.RelabelConfig{
+				{
+					Regex:  config.MustNewRegexp("(b.*)"),
+					Action: config.RelabelLabelKeep,
+				},
+			},
+			output: labels.FromMap(map[string]string{
+				"b1": "bar",
+				"b2": "baz",
+			}),
+		},
+		{
+			input: labels.FromMap(map[string]string{
+				"a":  "foo",
+				"b1": "bar",
+				"b2": "baz",
+			}),
+			relabel: []*config.RelabelConfig{
+				{
+					Regex:  config.MustNewRegexp("(b.*)"),
+					Action: config.RelabelLabelDrop,
+				},
+			},
+			output: labels.FromMap(map[string]string{
+				"a": "foo",
+			}),
+		},
+	}
+
+	for i, test := range tests {
+		res := Process(test.input, test.relabel...)
+
+		if !reflect.DeepEqual(res, test.output) {
+			t.Errorf("Test %d: relabel output mismatch: expected %#v, got %#v", i+1, test.output, res)
+		}
+	}
+}