Cross-reacting tumor-associated antigens were present in the cytoplasm of melanocytes in malignant melanoma. Both the leukocyte migration inhibition and the lymphocyte stimulation assays were used to determine the intracellular location(s) of these antigens in both human malignant melanoma and B-16 murine melanoma. The results of both assays indicate that this antigen(s) is associated with the membranous organelles, particularly the malanin granules, and is not found in the soluble components of the cytoplasm, as suggested by other studies.