Abstract: Nine of the ten rats orally administrated chloroquine phosphate 280 mg base/kg/d x3 died of intoxication. In comparison with the undrugged rats, mild embryotoxicity characterized by low live foetus rate and low average foetus weight was observed in rats subjected to chloroquine beginning from D8 of gestation at the dose of 70 mg/kg/d for 3 consecutive days (total dose=7x clinical total dose). As the regime increased to 140 mg/ kg/d x 3, the foetus skeleton dysmorphosis rate was 29% (16/55), significantly higher than that of the undrugged rats (P0.01). When rats were given pyrimethamine 7 mg/ kg/d x 3(total dose=10.5 x clinical total dose), the foetus skeleton dysmorphosis rate was 69.2% (27/39) and the dilation rate of cisterna fossae lateralis cerebri 29% (9/ 31). Both were significantly higher than those in the group subjected to chloroquine of 140 mg/kg/d x 3(=14 x clinical total dose). Orbital and vaginal hemorrhage was also noted in rats administered with chloroquine and pyrimethamine.