The influence of dietary zinc concentration on salicylate teratogenesis was studied in Wistar and Sprague-Dawley rats. Females were fed purified diets containing 0.4, 4.5, 9, 100, or 1,000 micrograms zinc/gm diet, or a stock diet (Purina Rat Chow) from day zero to day 21 of gestation, when they were killed and the fetuses were examined. On day 9, rats were given saline or 250, 500, or 750 mg sodium salicylate/kg body weight by gavage. Increasing drug dose caused increased frequency of malformed or resorbed fetuses, while increasing dietary zinc reduced the teratogenic effects of salicylate, but in different patterns in the two strains. The teratogenic effect of zinc deficiency also varied by strain. Statistical analysis showed that the frequency of malformed fetuses was significantly affected by levels of dietary zinc or salicylate dose, and interactions of zinc X salicylate and genetic strain X zinc. Frequency of resorption was affected by strain, zinc, salicylate, and interactions of strain X salicylate, zinc X salicylate, and strain X zinc X salicylate. Frequency of abnormal sites (malformed or resorbed) was affected by strain, zinc, salicylate, and interactions of strain X salicylate, zinc X salicylate, and strain X zinc X salicylate. The results suggest that marginal zinc deficiency in certain pregnant women might increase the possibility of salicylate teratogenicity.