Spermiation and epididymal maturation of spermatozoa were studied in the bonnet monkey (Macaca radiata) by light and scanning electron microscopy. The morphology, location, and release of residual body were observed during spermiation. Along the epididymal duct, the shape of spermatozoa changed, the constriction at the anulus disappeared, the marginal thickening diminished in length, and the cytoplasmic droplet regressed and moved toward the posterior end of the middle piece. Mature spermatozoa were very similar to those of other Cercopithecidae, and they showed a forward motility and a drop in eosin stainability.