Various 1-methyl- and 1, 3-dimethybarbiturates were prepared and their stimulatory effect on EHB-metabolism in the rat liver preparation were examined. The pretreatment of female rats with original barbiturates markedly accelerated the EHB-metabolism than that with 1-methylbarbiturates, and 1, 3-dimethylbarbiturates treatment had not such a stimulatory effect. It was demonstrated that such stimulatory effect of various N-substituted barbiturates on EHB-metabolism would be related to the substitution of N-position of barbituric acid ring.