The response of the astroglial population of the dentate gyrus molecular layer to removal of that region's primary afferent was investigated using Cajal's gold sublimate method. Deafferentation caused the astrocytes to hypertrophy, an effect which was detectable at 24 hr and maximal at 72-96 hr post-lesion. Following this, the astroglia entered a lengthy period of gradual atrophy. Counts of the astrocytes in the various sublayers of the molecular layer led to the conclusion that these cells migrate into denervated dendritic areas from neighboring, nondeafferented zones.