AbstractSingle oral doses of aldrin, dieldrin, and endrin, 1/2 LD50incorn oil, administered to pregnant golden hamsters on day 7, 8, or 9 of gestationcaused a high incidence of fetal death, congenital anomalies, and growthretardation. The most frequent defects were cleft palate, open eye, andwebbed foot, often occurring in combination. Pregnant CD1 mice given equivalent oral doses of each pesticide on day 9 of gestation showed similar anomalieswithout concurrent increase in fetal mortality or growth impairment.