Two human melanoma xenografts were compared with respect to their in vivo growth and metastatic potentials as well as glycosaminoglycan patterns. The less differentiated HT 168 tumor showed faster growth at primary sites and a more pronounced capacity for metastasis into the liver. Although chondroitin sulfate was the dominant glycosaminoglycan subtype in both tumors, the more invasive xenograft had a higher heparan sulfate/chondroitin sulfate (HS/CS) ratio. We suggest that tumor progression is influenced by this ratio in this human melanoma system.