Comparative studies were made of the effect of diethylstilbestrol on the utilization of dietary energy and protein by chicks fed diets containing glucose or corn oil as the major energy component. The metabolizable energy value of the high fat diet was decreased, but metabolic efficiency of energy utilization increased, by treatment of chicks with diethylstilbestrol. Restriction of energy intake amplified the depressive effect of diethylstilbestrol on metabolizable energy yield, and in itself caused a depression in metabolizable energy value of the high fat diet. Diethylstilbestrol treatment of chicks markedly decreased nitrogen retention at restricted levels of energy intake when the high fat diet was used. None of these effects was observed when glucose was the major dietary energy component. It is concluded that the effect of estrogens on certain metabolic processes is influenced by the form in which dietary energy is supplied.