The rubber seed oil is rich in polyunsaturated fat, with 36;linoleic acid, 24;lenolenic acid and some other unsaturated fatty acids. In recent years, we have demonstrated that the serum cholestrol and triglyceride levels of normal rats fed with rubber seed oil diet were lower than those of the rats fed with common diet. The lipidemia-reducing effect of the seed oil have been further demonstrated in both experimental hyperlipidemic animals ( rats and rabbits) and hyperlipoproteinemic patients. We have also found that some people who usually consumed this oil (for at least 6 months) had lower serum lipid levels ( either cholestrol or triglyceride) as compared with those who usually consumed other oils. Moreover, our study has also proved that rubber seed oil not only inhibited the development of aortic atherosclerosis in rabbits but also accelerated its regression to sme extent. Possible mechanisms of ther lipidemia-reducing effect of the oil have been discussed.