['To investigate the effects of human follicular fluid cultured with cumulus cells to inhibit the binding of spermatozoa to the zona pellucida of oocytes.', 'Controlled experimental laboratory study.', 'University gynecology unit.', 'Women undergoing assisted reproduction program and men visiting the subfertility clinics.', 'Culture medium and human follicular fluid were used to culture cumulus cells in vitro for specified time periods.', 'Zona binding capacity and motility of spermatozoa after incubation with cumulus cells treated culture medium or human follicular fluid.', 'Compared with the control medium, spent culture media after culturing cumulus cells for 3, 5, and 7 hours did not affect the motility and zona binding capacity of the treated spermatozoa. Significantly more spermatozoa treated with human follicular fluid that had been preincubated with cumulus cells for 5 and 7 hours bound onto hemizona in hemizona binding assay when compared with those preincubated in human follicular fluid without cumulus treatment. The hemizona index increased with the increase in the duration of cumulus cell treatment. Human follicular fluid with or without cumulus cells maintained sperm motility to similar extent for 3 hours.'] Do cumulus cells reduce the spermatozoa-zona binding inhibitory activity of human follicular fluid?