The glycosphingolipid compositions of Bomirski melanomas at different stages of differentiation, including Ab amelanotic melanoma (fast growing), Ma melanotic melanoma (slow growing), and MI hypomelanaotic melanoma (slow growing), were studied. The total concentration of lipid-bound sialic acid in Ab amelanotic melanoma was found to be much lower than those in Ma and MI melanomas (0.8 µg versus 1.4 µg and 1.4 µg/mg of dry tissue, respectively). The ganglioside patterns in melanoma tissues were composed mainly of three components, which were confirmed as NeuAcα2-3Galβl-4GIcβl-l'Cer (GM3), acetyl1-9-0-NeuAcα2-8NeuAcα2-3Galβ1-4Glcβl-1'Cer (9-0-acetyl-GD3), and NeuAcα2-8NeuAcα2-3Galβl-4Glcβ1-1 'Cer(GD3) by structural analysis and monoclonal antibody detections. However, the relative ratios of these gangliosides expressed in the different types of melanomas were completely different. The MI melanoma tissues contained GM3 as the predominant species (>90% of the total gangliosides) with very little of GD3 and 9-0-acetyl-GD3 gangliosides (<2% of the total gangliosides). In contrast, Ab amelanotic melanomas contained mainly 9-0-acetyl-GD3 (>27%) and GD3 (>51%) with lesser amounts of GM3. However, Ma melanoma had intermediate levels of GM3, GD3, and 9-0-acetyl GD3 The MI and Ma melanomas also contained monohexosylceramide (GL1) (about 60% as Galβ1-l'Cer and 40% as Glcβl-l'Cer in Ma and 30% as Galβl-1'Cer and 70% as Glcβ1-1'Cer in MI) and Galβl-4Glcβl-l'Cer as the predominant neutral glycosphingolipid species. In contrast, Ab melanoma tissues contained more GalNAcβ1-3GalNAcβ1-3Galαl-4Galβ1-4Glcβl-1'Cer (Gb5), Galαl-4Galβl-4Glcβl-l'Cer (Gb3), and GalNAcβl-3Galαl-4Galβl-4Glcβl-l'Cer (Gb4) than MI and Ma melanomas. Our data suggest that the expression of glycosphingolipids in hamster melanoma cells may be closely related to cell growth and the degree of differentiation, with slow growing, highly differentiated cells expressing GM3 and gli, and fast growing, undifferentiating cells having a preponderance of GD3, 9-0-acetyl-GD3, Gb5, Gb3, and Gb4. © 1989, American Association for Cancer Research. All rights reserved.