diff --git a/skimage/morphology/grey.py b/skimage/morphology/grey.py
index 19a4a346..4dfdbc3d 100644
--- a/skimage/morphology/grey.py
+++ b/skimage/morphology/grey.py
@@ -35,6 +35,11 @@ def erosion(image, selem=None, out=None, shift_x=False, shift_y=False):
     eroded : uint8 array
         The result of the morphological erosion.
 
+    Notes
+    -----
+    The lower algorithm complexity makes the `skimage.filter.rank.minimum`
+    more efficient for larger images and structuring elements.
+
     Examples
     --------
     >>> # Erosion shrinks bright regions
@@ -90,6 +95,11 @@ def dilation(image, selem=None, out=None, shift_x=False, shift_y=False):
     dilated : uint8 array
         The result of the morphological dilation.
 
+    Notes
+    -----
+    The lower algorithm complexity makes the `skimage.filter.rank.maximum`
+    more efficient for larger images and structuring elements.
+
     Examples
     --------
     >>> # Dilation enlarges bright regions