Rats have been fed for up to 2 years with either raw soya flour or control diets of heated soya flour or rat chow not containing soya flour. In addition, the rats received weekly injections of either a weak pancreatic carcinogen (azaserine) or control injection of saline. We found that rats fed a diet of raw soya flour and given weekly injections of azaserine developed benign and malignant neoplasms of the pancreas earlier in life and much more frequently than rats given raw soya flour alone, whereas azaserine alone in the dose used in this study did not produce pancreatic cancer. We conclude that raw soya flour sensitizes the pancreas to the action of azaserine.