diff --git a/README.md b/README.md
index 0034fac..7e5ab33 100644
--- a/README.md
+++ b/README.md
@@ -3,9 +3,19 @@
 
 ## Installing
 
+Install Python-OSC for output.
+
 > $ pip install python-osc
 
-Building the lexer and parser for Python3
+Install Antlr4 for input.
+
+> $ pip install antlr4-python3-runtime
+
+You must also install the ANTLR tool.  On a mac with homebrew, do:
+
+> $ brew install antlr
+
+Clone this repository and building the lexer and parser for Python3
 
 > $ antlr4 -Dlanguage=Python3 CommentMacro.g4