diff --git a/site/features.md b/site/features.md
index c4c4a3e7..b818e732 100644
--- a/site/features.md
+++ b/site/features.md
@@ -131,23 +131,23 @@ sharing it between applications:
 ### <a name="security"></a>Security
 
 In order to connect containers across untrusted networks, weave peers
-can be told to encrypt traffic by supplying a `-password` or
-`-passwordfile` option when launching weave, e.g.
+can be told to encrypt traffic by supplying a `-password` option or
+`WEAVE_PASSWORD` environment variable when launching weave, e.g.
 
     host1# weave launch -password wEaVe
 
 or
 
-    host1# weave launch -passwordfile /path/to/file
+    host1# export WEAVE_PASSWORD=wEaVe
+    host1# weave launch
 
-where the file must contain a single line like this:
-
-    WEAVE_PASSWORD=wEaVe
+_NOTE: The command line option takes precedence over the environment
+variable._
 
 The same password must be specified for all weave peers; it is a
 component in the creation of ephemeral session keys for connections
-between peers. See the
-[crypto documentation](how-it-works.html#crypto) for more details.
+between peers. See the [crypto documentation](how-it-works.html#crypto)
+for more details.
 
 ### <a name="host-network-integration"></a>Host network integration
 
diff --git a/weave b/weave
index 7eee3689..887a0c42 100755
--- a/weave
+++ b/weave
@@ -6,7 +6,7 @@ SCRIPT_VERSION="(unreleased version)"
 usage() {
     echo "Usage:"
     echo "weave setup"
-    echo "weave launch     [-password <password> | -passwordfile <path>] <peer> ..."
+    echo "weave launch     [-password <password>] <peer> ..."
     echo "weave launch-dns <cidr>"
     echo "weave connect    <peer>"
     echo "weave run        [--with-dns] <cidr> <docker run args> ..."
@@ -471,19 +471,15 @@ case "$COMMAND" in
         fi
         if [ "$1" = "-password" ] ; then
             [ $# -gt 1 ] || usage
-            PASSWORD_ARGS="-e WEAVE_PASSWORD=$2"
-            shift 2
-        elif [ "$1" = "-passwordfile" ] ; then
-            [ $# -gt 1 ] || usage
-            PASSWORD_ARGS="--env-file=$2"
+            WEAVE_PASSWORD="$2"
+            export WEAVE_PASSWORD
             shift 2
         fi
         # Set WEAVE_DOCKER_ARGS in the environment in order to supply
         # additional parameters, such as resource limits, to docker
         # when launching the weave container.
         CONTAINER=$(docker run --privileged -d --name=$CONTAINER_NAME \
-            -p $PORT:$PORT/tcp -p $PORT:$PORT/udp \
-            ${PASSWORD_ARGS:-"-e WEAVE_PASSWORD"} \
+            -p $PORT:$PORT/tcp -p $PORT:$PORT/udp -e WEAVE_PASSWORD \
             $WEAVE_DOCKER_ARGS $IMAGE -name $MACADDR -iface $CONTAINER_IFNAME "$@")
         with_container_netns $CONTAINER launch >/dev/null
         echo $CONTAINER