diff --git a/doc/parameter.md b/doc/parameter.md
index 228b11780..8d05b9b6c 100644
--- a/doc/parameter.md
+++ b/doc/parameter.md
@@ -46,6 +46,10 @@ Parameters for Tree Booster
 * colsample_bytree [default=1]
   - subsample ratio of columns when constructing each tree.
   - range: (0,1]
+* lambda [default=0]
+  - L2 regularization term on weights
+* alpha [default=0]
+  - L1 regularization term on weights
 
 Parameters for Linear Booster
 -----------------------------