The objective of this study was to summarize the English-language literature that addresses diabetes mellitus as a potential risk factor for the development of pancreatic cancer. Studies exploring the relation between diabetes and pancreatic cancer published between 1970 and 1999 were identified from a MEDLINE search and are summarized. They showed that diabetes mellitus occurs more frequently in patients with pancreatic cancer than in the general population. Most of the literature supports the view that diabetes of at least 5 years' duration increases the risk of subsequently developing pancreatic cancer. In addition, experimental forms of diabetes clearly affect the induction and growth of pancreatic cancer. The currently available literature thus suggests that diabetes is a risk factor for the subsequent development of pancreatic cancer.