Male rats were given liquid diets by pair-feeding for 24-30 days, and phosphatidylinositols in pancreas were analyzed as derivatives of diacylglycerols and fatty acids. Addition of arachidonic acid or changing the fat component (35 energy %) in the liquid diet from olive oil/corn oil to oil from Borago officinalis, which contains 22% gamma-linolenic acid, increased the fraction of arachidonoyl-containing species. This fraction was decreased by more than 50% by substituting ethanol for 36 of the 47 energy% provided by carbohydrate. A smaller difference between ethanol-fed and control rats was seen in the composition of phosphatidylcholines and phosphatidylethanolamines. There was no difference in the composition of phosphatidylinositols when fat, instead of ethanol, was used to substitute the 36 energy % in the diet containing olive oil/corn oil. Substituting ethanol for 28 of 35 energy% provided by fat as corn oil in a liquid diet had no effect on the fraction of arachidonoyl-containing species. The results indicate that the effect of ethanol on phosphatidylinositols in pancreas is not due to a deficiency of arachidonic acid, and that the effect of the ethanol-containing diet is not due to the lowered carbohydrate content. However, high contents of fat or of ethanol appear to be necessary for the effect.