Abstract: OBJECTIVE：To investigate teratogenicity of isoproturon in rats. METHODS：Pregnant Wistar rats were divided into 4 groups of 15 rats per group. Control group (peanut oil) and isoproturon (36.9，73.8 and 369.0 mg/kg) were administered by gavage once per day from day 6th to 15th of gestation. Rats were killed at the 20th day of gestation，maternal and embryonic developmental indicators were examined. RESULTS：Compared to the control group，all observation indicators of 36.9 and 73.8 mg/kg of isoproturon group were no statistically significant difference (P>0.05). On the 9^th day，the 369.0 mg/kg group showed signs of fatigue，fluffy back hair，and significantly lower body weight (P<0.01). The implantation counts and live fetus counts were lower (P<0.5)，dead embryos were increased and the average body weight of the litters were significantly less than that in the control group (P<0.5，P<0.01). Abnormalities were observed such as widened fontanelle，occipital ossifications，and incomplete and rib bending. The skeleton malformation rate of 27.78% was increased compared to the control group (P<0.05). CONCLUSION：Under our conditions，369.0 mg/kg of isoproturon treatment induced maternal toxicity and embryonic developmental toxicity in Wistar rats.

Key words: isoproturon, Wistar rats, maternal toxicity, embryonic developmental toxicity, teratogenicity