A simplified method of screening for antisperm antibodies has been previously described using rabbit antihuman immunoglobulin immunobeads (GAM beads). These reports have indicated a high correlation between the GAM bead and maximal individual isotype binding. However, preliminary data in our laboratory (using a 14% cut-off criterion) indicated a high frequency of samples with positive GAM bead, but negative individual isotype results. This study was conducted to evaluate more critically the use of the GAM bead for initial antisperm antibody screening. Immunobead binding tests were performed on 98 undiluted sera. The maximal binding of the individual isotype beads (IgG, IgA, or IgM) and the GAM beads were significantly correlated (r = 0.94, P = 0.0001). However, when results were categorized as positive or negative, there was a significantly lower frequency (P less than 0.05) of positive samples using the individual isotype (46.9%) than using the GAM approach (58.2%). These data support the hypothesis that, based on continuous percent binding, the GAM bead method produces results similar to individual isotype testing. However, when data are interpreted categorically, the results may differ significantly.