diff --git a/bin/start-slave.sh b/bin/start-slave.sh
index 26b5b9d462037b203344ff6902e73608f402236e..1082c09eb1044a3627661eb05b6bb4df18438500 100755
--- a/bin/start-slave.sh
+++ b/bin/start-slave.sh
@@ -1,4 +1,7 @@
 #!/usr/bin/env bash
+#
+# Usage: start-slave.sh <worker#> <master-spark-URL>
+#   where <master-spark-URL> is like "spark://localhost:7077"
 
 bin=`dirname "$0"`
 bin=`cd "$bin"; pwd`