The purpose of the present study was to evaluate the teratogenic potential of a zineb formulation. An initial toxicity study indicated that oral doses of 1,000 or 2,000 mg/kg/day adversely affected the weight gain of nonpregnant rats but not nonpregnant mice. In the teratology study pregnant rats and mice received daily oral doses of 0, 200, 632, or 2,000 mg/kg from day 6 of gestation until the day before C-section. Maternal welfare, as monitored by body weight and food consumption, was affected only in rats that received 2,000 mg/kg/day of the formulation. Evidence of embryo or fetal lethality was not present in rats or mice. However, fetuses from rats that received 2,000 mg/kg/day of the formulation had a reduced body weight. Some anomalies were significantly increased in rats that received 2,000 mg/kg/day of the formulation. These anomalies included hydrocephalus, split centra, incompletely ossified frontal bones, and enlarged occipital fontanel. None of the anomalies observed in mice were increased to a statistically significant level in any of the groups treated with the formulation. This study indicated that the zineb formulation produced anomalies in rats at doses which adversely affected maternal welfare. In addition, there was no evidence of teratogenicity in mice treated with similar doses.