Aim of the work: The present study aimed to evaluate the teratological effects of gamma-irradiation during three intervals of gestation; pre-implantation, organogenesis and fetal periods in rats. Material and methods: Four groups of pregnant rats were used in this study; the first one (GI) served as control. The second (GII), third (GIII) and fourth (GIV) groups were subjected to whole body γ-radiation at a sub-lethal single dose level of 4 Gy at the third day, 10^th day and 14^th day of gestation respectively.Pregnant rats were sacrificed at the 20^th day of gestation, implantation sites, resorption, embryonic death, fetal death, growth retarded fetuses, external malformations and skeletal malformation were recorded. Results: The results showed that whole body γ-irradiation caused resorption in the embryos of pregnant rats especially in those exposed during the pre-implantation period than the two other periods. The embryonic and fetal deaths were prominent in the fetuses maternally exposed to whole body γ-irradiation during the organogenesis period. The highest percentage of growth retarded fetuses was found in fetuses maternally exposed to γ-rays during the organogenesis period followed by fetuses maternally exposed to γ-irradiation during the fetal period and then fetuses maternally exposed to γ-irradiation during the pre-implantation period. The skeletal malformations as a result of γ-irradiation were mostly represented in less ossification in the skull bones, less ossification in the vertebral centra and wavy ribs. The most affected fetal skeleton was perceptive in GIII (fetuses maternally exposed to γ-irradiation during the organogenesis period) followed by GII and then GIV.