diff --git a/README.md b/README.md
index 1508959..778a1b1 100644
--- a/README.md
+++ b/README.md
@@ -19,6 +19,12 @@ ports: as from the docker syntax: 8080 or 8080:80, default "80", mandatory
 command: command to be executed, can be left blank
 ```
 
+Environment variables
+--------------
+```
+env_file: path to file containig a list of environment variables on the form FOO=BAR
+```
+
 
 
 Dependencies