Ricinus Communis L. was administered at doses of 10 and 20 mg/kg body weight to pregnant mice from the 6th to 15th day of pregnancy. The pregnant mice were sacrificed on the penultimate day of pregnancy and the gravid uterus of each was opened. Morphological examination of each uterine horn revealed 33.33 and 37.5% resorption of fetuses, and 22.22 and 32.5% fetal mortality. Fetal body weight and fetal length were Significantly reduced, their mean values being 2.60 + 0.22 and 1.90 + 0.16 (P < 0.05) gms and 16.20 = 0.80 (P < 0.01) and 14.36 + 0.71 (P < 0.01) mm. respectively. This corresponds to 2.70 0.86 g and 20.70 + 0.34 mm in the control group. Viable fetuses were freed from surrounding membranes and half the viable fetuses from each group were immersed in Bouin's fluid prior to sectioning and electron microscopic examination for visceral malformations. Visceral malformations recorded were, necrosis of brain cells, 10 and 15%, lungs of hard consistency, 5 and 10 %, hepatic damage 40 and 70 %, nephritis in 6 and 8 % respectively. The other half of the fetuses were fixed in ethyl alcohol prior to staining with alizarine red S for skeletal examination. Skeletal malformations noted were: incomplete ossification of the skull in 3.75 and 5.0% of each dose rate group, absence of One or more of the coccygeal vertebrae 12.5 and 31.25 %; irregular ribs in 7.5 and 12.5% absence of some metatarsal, metacarpal and phalangeal bones 31.25 and 37.5 %. The results of this investigation indicate that Ricinus Communis L. has a teratogenic effect on mouse embryos when administered orally to pregnant mice from the 6th to 15th day of gestation. It is suggested that the use of Ricinus Communis L. in should be avoided during pregnancy. It must be assumed that the effect of Ricinus Communis L. will be similar in other mammalian species until future investigation shows otherwise.