Morphine administration during pregnancy causes several behavioral abnormalities in offspring animals. In the present study the effects of maternal morphine consumption on development of neural tube in Wistar rats (250-300 g) were investigated. Female rats (n = 8 were crossed with male rats and pregnant ones were treated with oral morphine (0.01, 0.05 and 0.1 mg/ml of water) until the 10th day of pregnancy. On the day 10, the animals were anesthetized by diethyle ether and the embryos were taken out surgically. The embryos were fixed in formaline 10% for a week and then cross sectional procedure performed. The sections were stained with H&E. The results showed that: administration of morphine resulted in severe reduction in neural tube development in embryos. Morphine at a dose of 0.01 mg/ml showed the maximum effect. In conclusion, it is clear that morphine consumption in pregnant rats resulted in delay in neural tube development that may be true in humans.