SummarySperm obtained from groups of men with various semen profiles were incubated for 8 h in BWW medium containing human serum albumin to promote capacitation. Capacitation and the acrosome reaction were monitored by a chlortetracycline (CTC) fluorescence assay. Four distinct CTC patterns were observed on the sperm head. No significant difference was observed in the time‐course curve of these CTC patterns in sperm obtained from normozoospermic, asthenozoospermic and oligo‐zoospermic men. Spontaneous and A23187‐induced acrosome reactions were also comparable in these groups. However, in sperm obtained from teratozoospermic and polyzoospermic men, the increase in CTC pattern associated with capacitation appeared slower and sluggish. In these two groups, the induced acrosome reaction was also significantly lower when compared to that in the other three groups of men. In polyzoospermia, the spontaneous acrosome reaction was significantly lower when compared to all the other groups. Fresh sperm would not undergo the acrosome reaction following A23187 treatment. The results of this study indicate sluggish (defective) capacitation and inability of capacitated sperm to undergo induced acrosome reaction in teratozoospermic and polyzoospermic men as evaluated by the CTC m