Monoclonal antibodies submitted and exchanged by participating laboratories were analyzed serologically and biochemically in accordance with the goals and aims of the Workshop on Monoclonal Antibodies to Melanoma. Serological evaluation of the workshop panel revealed that when a variety of tumor and normal cell lines were tested by enzyme-linked immunoassay, a majority of antibodies reacted preferentially with melanoma cells. Indirect immunoprecipitation analysis of those antibodies that bound staphylococcal protein A provided molecular weight estimates for some antigens and additional information that suggested possible commonalities among antigens recognized by antibodies 9.2.27, 225.28S and 763.24TS. Competitive binding analyses demonstrated that antibodies 225.288 and 763.24TS bound separate and distinct epitopes from that recognized by antibody 9.2.27 on the core glycoprotein of melanoma-associated chondroitin sulfate proteoglycans. Immunoperoxidase staining of fresh frozen melanoma tissue with antibody 9.2.27 revealed a limited tissue distribution and preferential association with the cell surface of human melanoma cells.