Previously performed short-term (4-month) studies demonstrated that vitamins C and E, beta-carotene and selenium modulate growth of early putative preneoplastic acinar lesions induced in rat pancreas by azaserine. The present paper summarizes the results of long-term studies performed with azaserine-treated rats maintained on diets high in either beta-carotene, vitamins C and E or selenium. It appeared that rats given a diet high in beta-carotene, vitamin C or selenium, but not vitamin E, developed fewer pancreatic tumours than controls. The chemopreventive effects of these micronutrients were most pronounced when beta-carotene and/or selenium were given during the promotion phase of the carcinogenic process. Surprisingly, cell proliferation in azaserine-induced preneoplastic acinar lesions was higher in rats given beta-carotene and/or selenium via the diet in comparison to controls. It is considered unlikely that any antioxidant alone can be associated with protection against cancer. It is concluded that dietary supplementation of combinations of antioxidants may have practical application in chemoprevention of cancer.