The ultrastructure of tubular inclusions of caput and cauda epididymides were studied in rats that were fed only cowpeas from weaning (20-22 days old) to 130 days. The results showed significant (p < .001) fall in body weight and testicular, caput, and cauda epididymal weights in the cowpea-fed animals. Although the walls of the epididymides remained intact, the lumina of both segments showed cellular inclusions of various types amid sperm clumps. Unlike controls, where sperm flagella and headpieces were free-floating in lumina of both segments of epididymides, the experimental tubules showed cytoplasmic droplets containing trapped flagella at various stages of disintegration. Other inclusions included multilobular giant cells, lymphocytes, and membrane-bound amorphous bodies. It is proposed that these changes might be due to an altered immune response induced by lectins, one of the antinutritional factors found in cowpeas, which causes epididymal dysfunction and possibly renders these animals infertile.