Human spermatozoa were labelled with cationized ferritin and their interaction with cervical mucus or a capacitating medium enriched with 3% bovine serum albumin (BSA) was investigated by transmission electron microscopy. It was found that the sperm-coat was removed from the surface of spermatozoa after incubation in the BSA-enriched capacitating medium, as well as after crossing a column filled with cervical mucus. These results suggest that both media have a quantitatively similar action in removing the sperm-coat.