diff --git a/system/mpich/README b/system/mpich/README
index 12abd1860a..2dd223ac4c 100644
--- a/system/mpich/README
+++ b/system/mpich/README
@@ -8,3 +8,6 @@ The goals of MPICH are:
   and proprietary high-end computing systems (Blue Gene, Cray) and
 (2) to enable cutting-edge research in MPI through an easy-to-extend
   modular framework for other derived implementations.
+
+Note: mpich conflicts with openmpi. If you install both on the same
+system, unexpected results may occur.