Antiserum produced against a Mr 60,000 component (PPZA, purified pig zona antigen) isolated from porcine zonae was examined in respect to its species cross reactivity and contraceptive potential. Antiserum to PPZA produced precipitation layers of varying intensities on the zonae of all species tested. The degree of cross reactivity of anti-PPZA serum for zonae from various species, estimated by precipitation and immunofluorescent titrations, was in the order of human≥squirrel monkey>rabbit>rat>mouse. Percentages of 125I-labeled solubilized zonae from these species precipitated by a l:5000 dilution of the antiserum were 49, 27, 18, 18, and 0, respectively, for the pig, squirrel monkey, human, rabbit, and mouse. Pretreatment of intact zonae from human and squirrel monkey with PPZA antibody resulted in the in vitro inhibition of homologous sperm adherence to such treated zonae, thus demonstrating the contraceptive potential of PPZA antiserum in these two species. Similar treatments using the rabbit and mouse systems did not show any observable inhibition of homologous sperm adherence. Two-dimensional gel electrophoresis studies of radiolabeled porcine zona revealed a pattern of three major acidic macromolecules with average molecular weights of 92,000, 70,000, and 60,000, each of which exhibited extensive charge heterogeneity. Comparable studies performed on zonae from the human, squirrel monkey, rabbit, and mouse each revealed a species-specific pattern of two to four major families of acidic charge isomers with subunit molecular weights varying from 40,000–120,000. Human and squirrel monkey zonae each possessed one or more components similar to PPZA with respect to size and charge. Collectively, these electrophoretic and immunologic studies suggest that the zonae of pig, human, squirrel monkey, and rabbit each contain an acidic macromolecule which possesses antigenic determinants similar to those of PPZA.