Rat pancreatic cells were dissociated using a combined enzyme and EDTA method. Growhn on a plastic surface and then overlayed with collagen gel. Our studies have shown that exocrine pqncreatic cells grown in this way have the sbility to rearrange themselves into a three-dimensional organod structure in which well defined epithelial lumina have been identified by ultrastructural and light microscopic examination. This in vitro system has advantages in examining the cytodifferentiation of pancreatic cells and may be exploited in studying pancreatic carcinogenesis.