This study was conducted on determining the effects of phenytoin on the skeletal system of the fetuses of 13 Wistar Albino rats. The female rats were divided into two groups after the vaginal smear test: the group 1 (control group) included 6 individuals, whereas the group 2 (phenytoin group) comprised 7 animals. A dose of 25 mg/kg/day phenytoin was administered intraperitoneally to pregnant rats on the 8th-10th days of pregnancy and fetuses were obtained by C-section on the 20th day. A number of 82 fetuses were observed by double staining technique. Their lengths and weights were measured, revealing the statistically significant differences between the two groups (p < 0.001). The lengths of the fetuses in the group 2 were determined as to be 14% shorter and the weights 13% lower compared to those in the group 1. Similarly, number of the fetuses obtained in one gestation decreased 9% in the group 2. Ossification of the skull bones in the fetuses of the group 2 was observed eminently to be deteriorated through using dissection microscope and inspection. Costal separation anomaly was observed in the 10 fetuses of the group 2. The separated-laterally located costal components were not attached to the costal arch. Shape malformations in the last two ribs and wide angularity, particularly in the last six ribs, were also determined.