The effects of perinatal exposure of Wistar-derived albino rats to chloroquine were studied. Chronic exposure to 10 mg/kg of chloroquine phosphate during intra-uterine and postnatal life resulted in a marked decrease in neonatal and postweaning body and organ weights. The fasting blood glucose level was significantly elevated at 8 weeks of age in animals exposed to chloroquine. The observed growth retardation suggested transplacental poisoning and poisoning through milk transfer. The elevation in blood sugar level could be a consequence of possible ultrastructural and biochemical alterations of pancreatic B cells.