Ten primary and 6 metastatic mucosal melanoma lesions were tested, utilizing the immunoperoxidase reaction with a panel of 26 monoclonal antibodies (MAbs). The latter included MAbs recognizing membrane-bound and cytoplasmic-melanoma-associated antigens, adhesion molecules and their receptors, and HLA Class-I and Class-II antigens. The melanoma lesions displayed differential reactivity with the panel of MAbs. Mucosal melanoma lesions differ from other types of melanoma in their antigenic profile, since they are the only type of melanoma to display a higher expression of p97 MAA, CEA-MAA and NGF-R in primary lesions than in metastatic ones. Furthermore, the pattern of HMW-MAA expression in mucosal melanoma lesions is different from that in nodular and uveal melanoma lesions and only partly resembles that observed in acral lentiginous melanoma lesions. Like other types of melanoma, mucosal melanoma lesions display a heterogeneous expression of HLA antigens, a selective loss of reactivity with some of the anti-HLA Class-I MAbs and a higher frequency of abnormalities in HLA Class-I antigen expression in metastatic than in primary lesions. Expression of HMW-MAA, 110-kDa MAA, p97 MAA, CEA-MAA, NGF-R and GD2 ganglioside in primary melanoma lesions was found to be associated with a poor prognosis. Although preliminary in nature, these results suggest that analysis of mucosal melanoma lesions with MAbs, in conjunction with information about the clinical course of the disease, will contribute to determine the biological and clinical significance of the distinct characteristics of the antigenic profile of mucosal melanoma lesions.