This study was undertaken to observe the effect of sesame in the diet of rats (Splague Dowley). Comparisons were made of weight gains, organ weights and the cholesterol, phospholipid and triglyceride content of the blood serum and liver tissue. Rats weighing 67-80 g were used for the <case A> study, while rats weighing 160-165 g were used in the <Case B> study. In the both studies, the experimental animals were fed on sesame mixtures for 24 weeks. The <Case A> study was conducted to determine the effect of sesame hulls which are known to contain a high proportion of oxalic acid and phytic acid, which are toxic substances causing various physical disorders. The rats were divided into four groups, a control group which was fed on a standard diet and three groups fed with 20%, 10% and 5% mixtures of sesame seed hulls respectively. The <Case B> study was designed to observe the same effect, but in this case the rats were divided into two groups, one fed with a 5% mixture of whole sesame seeds and the other with a 5% mixture of dehulled seeds. The results are as follows: 1) An examination of weight gains showed that group I and II which were fed on 20% and 10% mixture of sesame hulls were significantly retarded in comparison with the control group(P<0. 05). 2) Comparisons of organ weights, group I (20% mixture) showed relatively lower weights(P<0.05). 3) The cholesterol content of the blood serum and liver tissue of group I (20% mixture) and group II (10% mixture) were significantly higher than that of the control. 4) The group fed on the whole sesame seed diet and that fed on the dehulled seed diet differed significantly from each other. 5) With the results stated above, the investigators could observe that a high content of sesame hulls in the diet caused retardation in growth and might be the cause of many physical disorders. Though these effects are not important in Korea at present, the increasing intake of sesame seeds and oils indicates that it may become an important problems.