A high molecular weight secretion product of cell lines established from duct cell-derived human pancreatic adenocarcinomas was investigated in this study. After metabolic labeling and molecular sieve chromatography of culture medium, a product appeared in the void volume of a Superose 6 column that could be labeled with [3H]glucosamine, but not with [35S]sulfate. After further purification by anion exchange chromatography it was analyzed and demonstrated to be hyaluronan (HA). CsCl density gradient centrifugation revealed a density of 1.45 g/cm3 in a 4 M guanidinium hydrochloride solution. [3H]Glucosamine-labeled material could be degraded by digestion with hyaluronidase from two sources, but not with heparitinase I or chondroitinase AC. Sugar analysis revealed glucuronic acid and glucosamine at a molar ratio of 1:1. When the amount of HA synthesized by different pancreatic adenocarcinoma cell lines was compared, the values of the cell lines PaTu 8902 and PaTu II were about five- to tenfold higher than those of the lines PaTu 8988s, PaTu 8988t or HPAF, but an order of magnitude lower than in murine 3T3 fibroblasts. HA synthesis per cell decreased with increasing cell density. In serum-free cultures of cell lines with high HA synthesis it was 3 to 5 times higher compared to cultures that were supplemented with serum. We conclude that pancreatic adenocarcinoma cells secrete hyaluronan and thus contribute to the extracellular matrix of the tumor tissue. In pancreatic carcinoma cells, regulation of HA biosynthesis seems not to be positively correlated to proliferation as has been demonstrated for fibroblasts.