In order to study the effect of riboflavin on lipid peroxidation in rats, randomized block design was used to study the effect of different riboflavin levels on the riboflavin status and lipid peroxidation of S.D. rats. The rats fed with riboflavin deficient diets for 6 weeks had higher levels of BGRAC, blood malondialdehyde and lower levels of GSH than those with riboflavin sufficient diets. The RBC SOD activity is also reduced in riboflavin deficiency rats. It is concluded that riboflavin deficiency increases the extent of lipid peroxidation.