This study was conducted to determine the fertility predictive value of acrosome reaction rates and indices (induced minus control) of human spermatozoa. By comparison these outcomes with in vitro fertilization success. The effect of oocyte-cumulus complex exposure on the induction of the acrosome reaction was also analyzed. Patients attending our assisted reproduction unit for infertility treatment were included in the study. Acrosome reactions were determined on ethanol-permeabilized smears using FITC-conjugated Pisum sativum agglutinin. The acrosome reaction inducing agent used was calcium ionophore A23187 (10 microM/ml).Poor correlations were found between all the acrosome reaction rates and indices and in vitro fertilization. The presence of oocyte-cumulus complexes had no effect on the spontaneous acrosome reactions, but had a significant effect on the inducibility of the acrosome reaction. Exposure to oocyte-cumulus complexes resulted in the mean percentage sperm induced to be 7.8% (SE = 3.1%) higher compared to the control samples.Acrosome reaction rates and indices were therefore found to have no significant value in the prediction of male fertility and/or in vitro fertilization success. This study did, however, show that exposure to oocyte-cumulus complexes significantly increases the inducible sperm population.