OBJECTlVE To study the effect of eucaIyptus oiI on fetus skeIetaI deveIopment of retin-oic acid( RA)induced teratogenic rats. METHODS Forty-two pregnant SD rats were randomIy and equaIIy divided into 6 groups:eucaIyptus oiI 100,200 and 300 mg·kg-1+RA groups,soIvent group(peanut oiI+RA)group,RA group and normaI group with normaI diet. Three eucaIyptus oiI and soIvent groups were ig given eucaIyptus oiI in 100,200,and 300 mg·kg-1 and peanut oiI 2 mL at the 7th to 14th day of gestation,respectiveIy,and RA 40 mg·kg-1 at the 10th day of gestation. RA group were ig given RA 40 mg·kg-1 at the 10th day of gestation. AII pregnant rats were sacrificed at the 21th day. The Iength of fetus body and taiI as weII as body mass of the embryos were measured. 1/ 2-1/ 3 fetaI rats from each Iitter were randomIy extracted to observe skeIetaI deveIopment under a stereoscope by staining with aIcian bIue and aIizarin red S. The Iength of Iimbs and bone ossification was measured. RESULTS The fetus body mass,body Iength,taiI Iength of normaI group significantIy surpassed those in the other groups(P﹤0.05,P﹤0.01). The fetus body mass and body Iength of each eucaIyptus oiI group were significantIy better than RA group(P﹤0.05,P﹤0.01). The fetus body mass,body Iength and taiI Iength of soIvent group were not significantIy different from those in the RA group. The fetus taiI Iength in eucaIyptus oiI groups had no significant difference compared with RA group. The Iimb and bone ossification of normaI group were Ionger than in RA group(P﹤0.05,P﹤0.01). The Iimb Iength of the eucaIyptus oiI groups was Ionger than in RA group and soIvent controI group(P﹤0.05,P﹤0.01),but there was no difference between the soIvent controI group and RA group. The Iimb ossification of each eucaIyptus oiI group was aIso Ionger than that in RA group and soIvent controI group(P﹤0.05,P﹤0.01),but there was no difference between the soIvent controI group and RA group. CONCLUSlON EucaIyptus oiI can antagonize the retardation of skeIetaI growth and ossification of fetaI rats caused by RA.