The phenolic oxidant 2(3)-tert-butyl-4-hydroxyanisole (BHA), has been found to induce carcinogenic response in the forestomach of Syrian golden hamsters and other rodent species. In this study, the differential effects of BHA was determined in the forestomach of Syrian golden hamsters from different sources. Lakeview (LVG) Syrian golden hamsters were fed diets containing 2% BHA incorporating into semipurified, Purina and Oriental M diets for 30 weeks. No papilloma or severe hyperplasia was found in any of the experimental or control groups. A significant increase in the number of hamsters having mild hyperkeratosis and mild hyperplasia was found in the semipurified-BHA group. In contrast, greater than 82 and 90% of the Misaki hamsters developed moderate to severe hyperplasia, and 64 and 80% had papilloma in the forestomach of the 1 and 2% BHA groups respectively. The control group had one animal with moderate hyperplasia that was confined to the limiting ridge. The obvious difference in the appearance of the two strains of hamsters is their body weight. The Misaki hamsters were 20-30% heavier than the LVG hamsters from the beginning and toward the end of the experiment. These results showed that the diet alone was not the reason for the failure of BHA to induce forestomach papilloma in the LVG hamsters. A much longer latent period may be required for the LVG hamsters to develop neoplastic lesions in the forestomach. The high sensitivity of the Misaki hamsters provides a valuable tool to study weak nongenotoxic carcinogens.