diff --git a/build_image b/build_image
index a67bc3163d..e5891f9ed2 100755
--- a/build_image
+++ b/build_image
@@ -62,8 +62,6 @@ show_help_if_requested "$@"
 # not needed for the typical developer workflow.
 DEFINE_integer build_attempt 1 \
   "The build attempt for this image build."
-DEFINE_boolean fast ${FLAGS_TRUE} \
-  "Use the parallel_emerge wrapper script."
 DEFINE_integer jobs "${NUM_JOBS}" \
   "How many packages to build in parallel at maximum."
 DEFINE_boolean replace ${FLAGS_FALSE} \
diff --git a/build_library/build_image_util.sh b/build_library/build_image_util.sh
index 6f9fe65474..3e6b418e05 100755
--- a/build_library/build_image_util.sh
+++ b/build_library/build_image_util.sh
@@ -102,11 +102,7 @@ emerge_to_image() {
   test -n "$mask" || die "PROD_INSTALL_MASK not defined"
 
   local emerge_cmd
-  if [[ "${FLAGS_fast}" -eq "${FLAGS_TRUE}" ]]; then
-    emerge_cmd="$GCLIENT_ROOT/chromite/bin/parallel_emerge --board=$BOARD"
-  else
-    emerge_cmd="emerge-$BOARD"
-  fi
+  emerge_cmd="emerge-$BOARD"
   emerge_cmd+=" --root-deps=rdeps --usepkgonly -v"
 
   if [[ $FLAGS_jobs -ne -1 ]]; then
diff --git a/build_packages b/build_packages
index 59969e5f84..728c500c64 100755
--- a/build_packages
+++ b/build_packages
@@ -20,10 +20,6 @@ DEFINE_boolean getbinpkg "${FLAGS_TRUE}" \
   "Download binary packages from remote repository."
 DEFINE_boolean noworkon "${FLAGS_FALSE}" \
   "Don't force-build workon packages."
-DEFINE_boolean showoutput "${FLAGS_FALSE}" \
-  "Show all output from parallel_emerge."
-DEFINE_boolean withautotest "${FLAGS_TRUE}" \
-  "Build autotest client code."
 DEFINE_boolean fetchonly "${FLAGS_FALSE}" \
   "Don't build anything, instead only fetch what is needed."
 
@@ -39,8 +35,6 @@ up by the build_image script to put together a bootable Chrome OS image.
 
 If [packages] are specified, only build those specific packages (and any
 dependencies they might need).
-
-For the fastest builds, use --nowithautotest --noworkon.
 "
 show_help_if_requested "$@"
 
@@ -53,8 +47,6 @@ DEFINE_boolean toolchainpkgonly $FLAGS_FALSE \
   "Use binary packages only for the board toolchain."
 DEFINE_string accept_licenses "" \
   "Licenses to append to the accept list."
-DEFINE_boolean fast "${DEFAULT_FAST}" \
-  "Use the parallel_emerge wrapper script."
 DEFINE_integer jobs "${NUM_JOBS}" \
   "How many packages to build in parallel at maximum."
 DEFINE_boolean norebuild "${FLAGS_FALSE}" \
@@ -93,11 +85,6 @@ UPDATE_ARGS=( --regen_configs )
 if [[ -n ${FLAGS_accept_licenses} ]]; then
   UPDATE_ARGS+=( --accept_licenses "${FLAGS_accept_licenses}" )
 fi
-if [ "${FLAGS_fast}" -eq "${FLAGS_TRUE}" ]; then
-  UPDATE_ARGS+=( --fast )
-else
-  UPDATE_ARGS+=( --nofast )
-fi
 if [ "${FLAGS_usepkg}" -eq "${FLAGS_TRUE}" ]; then
   UPDATE_ARGS+=( --usepkg )
   if [[ "${FLAGS_getbinpkg}" -eq "${FLAGS_TRUE}" ]]; then
@@ -138,15 +125,7 @@ fi
 
 # Setup all the emerge command/flags.
 EMERGE_FLAGS=( -uDNv --backtrack=30 --select )
-
-if [[ "${FLAGS_fast}" -eq "${FLAGS_TRUE}" ]]; then
-  EMERGE_CMD=(
-    "${CHROMITE_BIN}/parallel_emerge"
-    --board=${FLAGS_board}
-  )
-else
-  EMERGE_CMD=( "emerge-${FLAGS_board}" )
-fi
+EMERGE_CMD=( "emerge-${FLAGS_board}" )
 if [[ "${FLAGS_fetchonly}" -eq "${FLAGS_TRUE}" ]]; then
   EMERGE_CMD+=( --fetchonly )
 fi
@@ -174,11 +153,6 @@ fi
 if [[ "${FLAGS_norebuild}" -eq "${FLAGS_FALSE}" ]]; then
   EMERGE_FLAGS+=( --rebuild-if-unbuilt )
 fi
-if [[ "${FLAGS_showoutput}" -eq "${FLAGS_TRUE}" && \
-      "${FLAGS_fast}" -eq "${FLAGS_TRUE}" ]]; then
-  # Only parallel_emerge supports --show-output.
-  EMERGE_FLAGS+=( --show-output )
-fi
 
 # Build cros_workon packages when they are changed.
 CROS_WORKON_PKGS=()
diff --git a/common.sh b/common.sh
index b2f055276d..84b5bbee95 100644
--- a/common.sh
+++ b/common.sh
@@ -390,9 +390,6 @@ if [[ -f ${GCLIENT_ROOT}/src/scripts/.default_board ]]; then
   fi
 fi
 
-# Disable --fast in most commands
-DEFAULT_FAST=${FLAGS_FALSE}
-
 # Directory to store built images.  Should be set by sourcing script when used.
 BUILD_DIR=
 
diff --git a/sdk_lib/make_chroot.sh b/sdk_lib/make_chroot.sh
index 7cfb4d590f..9d7ce0f39a 100755
--- a/sdk_lib/make_chroot.sh
+++ b/sdk_lib/make_chroot.sh
@@ -40,8 +40,6 @@ DEFINE_boolean getbinpkg $FLAGS_TRUE \
   "Download binary packages from remote repository."
 DEFINE_boolean delete $FLAGS_FALSE "Delete an existing chroot."
 DEFINE_boolean replace $FLAGS_FALSE "Overwrite existing chroot, if any."
-DEFINE_boolean fast "${DEFAULT_FAST}" \
-  "Use the parallel_emerge wrapper script."
 DEFINE_integer jobs "${NUM_JOBS}" \
   "How many packages to build in parallel at maximum."
 DEFINE_string stage3_path "" \
@@ -358,11 +356,6 @@ if [[ ${FLAGS_usepkg} -eq ${FLAGS_TRUE} ]]; then
 else
   UPDATE_ARGS+=( --nousepkg )
 fi
-if [[ ${FLAGS_fast} -eq ${FLAGS_TRUE} ]]; then
-  UPDATE_ARGS+=( --fast )
-else
-  UPDATE_ARGS+=( --nofast )
-fi
 if [[ "${FLAGS_jobs}" -ne -1 ]]; then
   UPDATE_ARGS+=( --jobs=${FLAGS_jobs} )
 fi
diff --git a/setup_board b/setup_board
index 6ce046518b..a88cff2489 100755
--- a/setup_board
+++ b/setup_board
@@ -37,8 +37,6 @@ DEFINE_string getbinpkgver "" \
   "Use binary packages from a specific version."
 DEFINE_boolean toolchainpkgonly $FLAGS_FALSE \
   "Use binary packages only for the board toolchain."
-DEFINE_boolean fast "${DEFAULT_FAST}" \
-  "Use the parallel_emerge wrapper script."
 DEFINE_integer jobs "${NUM_JOBS}" \
   "How many packages to build in parallel at maximum."
 DEFINE_boolean latest_toolchain $FLAGS_FALSE \
@@ -140,11 +138,6 @@ get_board_and_variant $FLAGS_board $FLAGS_variant
 
 # Before we can run any tools, we need to update chroot
 UPDATE_ARGS="--toolchain_boards=${BOARD}"
-if [ "${FLAGS_fast}" -eq "${FLAGS_TRUE}" ]; then
-  UPDATE_ARGS+=" --fast"
-else
-  UPDATE_ARGS+=" --nofast"
-fi
 if [ "${FLAGS_usepkg}" -eq "${FLAGS_TRUE}" ]; then
   UPDATE_ARGS+=" --usepkg"
   if [[ "${FLAGS_getbinpkg}" -eq "${FLAGS_TRUE}" ]]; then
diff --git a/update_chroot b/update_chroot
index add4b3dbd8..7a2b419150 100755
--- a/update_chroot
+++ b/update_chroot
@@ -28,8 +28,6 @@ show_help_if_requested "$@"
 # The following options are advanced options, only available to those willing
 # to read the source code. They are not shown in help output, since they are
 # not needed for the typical developer workflow.
-DEFINE_boolean fast ${DEFAULT_FAST} \
-  "Use the parallel_emerge wrapper script."
 DEFINE_integer jobs "${NUM_JOBS}" \
   "How many packages to build in parallel at maximum."
 DEFINE_boolean skip_toolchain_update $FLAGS_FALSE \
@@ -148,10 +146,6 @@ fi
 
 # Perform an update of coreos-devel/sdk-depends and world in the chroot.
 EMERGE_CMD="emerge"
-CHROMITE_BIN="${GCLIENT_ROOT}/chromite/bin"
-if [ "${FLAGS_fast}" -eq "${FLAGS_TRUE}" ]; then
-  EMERGE_CMD="${CHROMITE_BIN}/parallel_emerge"
-fi
 
 # In first pass, update portage and toolchains. Lagged updates of both
 # can cause serious issues later.
@@ -175,6 +169,7 @@ if [[ "${FLAGS_skip_toolchain_update}" -eq "${FLAGS_FALSE}" && \
 fi
 
 # Build cros_workon packages when they are changed.
+CHROMITE_BIN="${GCLIENT_ROOT}/chromite/bin"
 for pkg in $("${CHROMITE_BIN}/cros_list_modified_packages" --host); do
   EMERGE_FLAGS+=" --reinstall-atoms=${pkg} --usepkg-exclude=${pkg}"
 done