Radioimmunoscintigraphy with monoclonal antibodies (MoAbs) to melanoma associated antigens is a new technique that can be used as an additional test to detect ocular melanomas in clinically difficult cases. Immunoscintigraphy with 99mtechnetium-labelled monoclonal antibody fragments of MoAb 225.28S in 14 patients with melanoma yielded a positive image in only six cases (43%). The expression of high molecular weight melanoma-associated antigen (HMW-MAA) was immunohistochemically assessed in melanoma tissue obtained from these 14 patients to find a possible correlation between the results of immunoscintigraphy and expression of the HMW-MAA. The melanoma tissues were immunohistochemically stained by a sensitive immunoperoxidase procedure with three different monoclonal antibodies to the HMW-MAA: 225.28S, Mel-14, and AMF-6. Expression of the antigen detected by MoAb 225.28S was found in 13 of 14 melanomas; the MoAbMel-14 reacted positively with all 14 melanomas; staining with MoAb AMF-6 was achieved in 10 melanomas. No correlation was found between the immunohistochemical staining results, the conventional histopathological findings, and the immunoscintigraphic results. The immunohistochemical staining results suggest that anti-HMW-MAA MoAbs bind to the melanoma tissue and are therefore potentially suitable for immunoscintigraphy.