Monoclonal antibodies were raised against cultured melanoma cells and selected for their reactivity with melanoma-associated antigens expressed on various melanoma lines. Of 34 monoclonal antibodies, which were all reacting with melanoma lines only 19 antibodies bound to fresh melanoma tissue. Of the 19 antibodies 10 displayed a broad cross-reactivity with normal cells and structures, whereas 9 had a restricted reactivity. Of these antibodies five types were defined, which detected antigens (nevocellular I, nevocellular II, neural, endothelial, basal cell), which were found on certain normal tissues and structures and on certain tumor phenotypes. On the basis of an extensive study on melanoma biopsies of different stages it became evident, that the endothelial, the basal cell and also HLA-DR antigens were significantly more expressed in high risk melanomas. The basal cell antigen was preferentially expressed in locoregional metastases. By immunization with fresh melanoma biopsies different specificities of monoclonal antibodies were obtained as compared to immunization with established cell lines.