diff --git a/README.md b/README.md
index 806e572..7654a18 100644
--- a/README.md
+++ b/README.md
@@ -34,6 +34,23 @@ https://github.com/bbatsov/prelude/raw/master/utils/installer.sh
 
 You can now power up your Emacs, sit back and enjoy Prelude.
 
+There are two environment variables you can use to control the 
+source repository and the installation directory. To change the 
+installation directory:
+
+`PRELUDE_INSTALL_DIR="$HOME/.emacs.d" && 
+ curl -L
+https://github.com/bbatsov/prelude/raw/master/utils/installer.sh
+| sh`
+
+To change the source repository:
+
+`PRELUDE_URL="https://github.com/yourname/prelude.git" &&
+ curl -L
+https://github.com/bbatsov/prelude/raw/master/utils/installer.sh
+| sh`
+
+
 ## Would you like to know more?
 
 Check out the [Prelude's project page](http://batsov.com/prelude) for
diff --git a/utils/installer.sh b/utils/installer.sh
index 56c26c6..011261e 100755
--- a/utils/installer.sh
+++ b/utils/installer.sh
@@ -1,5 +1,5 @@
-PRELUDE_INSTALL_DIR="$HOME/.emacs.d"
-PRELUDE_URL=https://github.com/bbatsov/prelude.git
+[ -z "$PRELUDE_INSTALL_DIR" ] && PRELUDE_INSTALL_DIR="$HOME/.emacs.d"
+[ -z "$PRELUDE_URL" ] && PRELUDE_URL=https://github.com/bbatsov/prelude.git
 
 if [ -d $PRELUDE_INSTALL_DIR/prelude ]
 then