Gonadoliberine in clinical practice is administered to stimulate reproduction. The authors examined the influence of the drug on the foetus because of its possibility to be applied to pregnant animals. It was found that Gonadoliberine given during pregnancy had a negative effect on its course and neonates might show a physical immaturity. The intensity of immaturity was a reverse proportional to the amount of the drug. However, no congenital defects were observed in the foetuses.