The relevance of lipoprotein-glycosaminoglycan interactions on the proteoglycan metabolism was investigated. The following results were obtained: 1) Biosynthesis of [35S]proteoglycans by cultured human skin fibroblasts and their distribution to different compartments are neither affected by preincubation of the cells with homologous LDL nor by their presence. The internalisation of LDL was evidenced by a marked depression of [14C]cholesterol synthesis from [1-(14)C]-acetate. 2) Under the conditions of endocytosis experiments the formation of insoluble proteoglycan-LDL complexes is insignificant. Endocytosis and degradation of exogenous proteoglycans by skin fibroblasts or arterial smooth muscle cells proceed at normal rates in the presence of low or excess LDL concentrations. 3) From the results it may be concluded, that internalized LDL and their degradation products neither influence the synthesis and distribution of sulfated proteoglycans nor control expression and function of proteoglycan specific cell surface receptors.