Seventeen primary and sixteen metastatic surgically removed melanoma lesions were stained indirect immunoperoxidase with anti-GD3, GD2, GD2 + GD3, and acetyl-GD3 monoclonal antibodies. In primary melanoma 94%, 59%, 53%, and 76% of the lesions tested were evidently stained by anti-GD3, GD2, GD2 + GD3, and acetyl-GD3 monoclonal antibodies, respectively. In metastatic lesions 94%, 63%, 31%, and 31% of the lesions were stained by monoclonal antibodies, respectively. Expression of GD2 + GD3 and acetyl-GD3 were evidently decreased from primary lesion to metastatic lesions. And the heterogeneity of positive cells in lesions were noteworthy. It is also interesting that expression of ganglioside in ALM were much decreased than that of ganglioside in NM.