Several recent studies strongly suggest that pancreatic cancer causes in the majority of patients type II diabetes that can be improved or cured by subtotal pancreatectomy. Our studies have shown alterations of hormone production in islets adjacent to cancer and the presence of abnormal endocrine cells, including insulin, glucagon, somatostatin, pancreastatin and serotonin, by tumor cells. Alterations of insulin-like amyloid polypeptides (IAPP) were found in islets surrounding the tumor and their production in some cancer cells. A significantly higher IAPP level was found in the plasma of pancreatic cancer patients than in those with other types of cancers. It appears that an increase in plasma IAAP could present an early marker for pancreatic cancer.