Pregnant golden hamsters (Mesocricetus auratus) were irradiated on specified gestation days (6th, 8th, 10th and 12th day p.c.) with a single dose of 200 R. 1 day prior to term, on the 15th day p.c, the offspring was removed from the uterus. The ophthalmic system showed a great radiosensitivity during the embryonic and the early fetal period. The critical stages of severe eye malformations were the 8th and 10th intrauterine days. The observed damages were: complete absence of the eye, anopthalmia with abortive rudiments and microphthalmia. Parts of the ophthalmic system of neuroectodermal origin showed the most severe malformations. Irradiation at the fetal stage (12th day p.c.) affected compartments of the eye which originate in the mesenchyme. Other parts of the eye showed only few anomalies on the histological level. On the 12th day p.c. the trias microphthalmia, aplasia of the anterior eye segment, and lens anomalies could be seen in irradiated animals.