diff --git a/skimage/morphology/cmorph.pyx b/skimage/morphology/cmorph.pyx
index 05dba333..2e0fa88a 100644
--- a/skimage/morphology/cmorph.pyx
+++ b/skimage/morphology/cmorph.pyx
@@ -12,7 +12,30 @@ def _dilate(np.ndarray[np.uint8_t, ndim=2] image,
            np.ndarray[np.uint8_t, ndim=2] selem,
            np.ndarray[np.uint8_t, ndim=2] out=None,
            char shift_x=0, char shift_y=0):
+    """Return greyscale morphological erosion of an image.
 
+    Morphological erosion sets a pixel at (i,j) to the minimum over all pixels
+    in the neighborhood centered at (i,j). Erosion shrinks bright regions and
+    enlarges dark regions.
+
+    Parameters
+    ----------
+    image : ndarray
+        Image array.
+    selem : ndarray
+        The neighborhood expressed as a 2-D array of 1's and 0's.
+    out : ndarray
+        The array to store the result of the morphology. If None is
+        passed, a new array will be allocated.
+    shift_x, shift_y : bool
+        shift structuring element about center point. This only affects
+        eccentric structuring elements (i.e. selem with even numbered sides).
+
+    Returns
+    -------
+    eroded : uint8 array
+        The result of the morphological erosion.
+    """
     cdef Py_ssize_t rows = image.shape[0]
     cdef Py_ssize_t cols = image.shape[1]
     cdef Py_ssize_t srows = selem.shape[0]
@@ -67,6 +90,31 @@ def _erode(np.ndarray[np.uint8_t, ndim=2] image,
           np.ndarray[np.uint8_t, ndim=2] selem,
           np.ndarray[np.uint8_t, ndim=2] out=None,
           char shift_x=0, char shift_y=0):
+    """Return greyscale morphological dilation of an image.
+
+    Morphological dilation sets a pixel at (i,j) to the maximum over all pixels
+    in the neighborhood centered at (i,j). Dilation enlarges bright regions
+    and shrinks dark regions.
+
+    Parameters
+    ----------
+
+    image : ndarray
+        Image array.
+    selem : ndarray
+        The neighborhood expressed as a 2-D array of 1's and 0's.
+    out : ndarray
+        The array to store the result of the morphology. If None, is
+        passed, a new array will be allocated.
+    shift_x, shift_y : bool
+        shift structuring element about center point. This only affects
+        eccentric structuring elements (i.e. selem with even numbered sides).
+
+    Returns
+    -------
+    dilated : uint8 array
+        The result of the morphological dilation.
+    """
 
     cdef Py_ssize_t rows = image.shape[0]
     cdef Py_ssize_t cols = image.shape[1]