The present investigation was conducted to determine if rats can recognize the essential fatty acid (EFA) in the diet. Weanling rats were pre-fed a 30% hydrogenated coconut oil (30HCO) diet containing 1% cholesterol for 2 or 4 weeks to produce EFA deficiency, then allowed to choose between the fat-free (FF) diet and the 0.5, 1.0, or 2.0% corn oil diet, and between the 0.5% HCO diet and 0.5% corn oil diet. Rats pre-fed the 30HCO diet for 2 weeks selected the corn oil-containing diets for a few days at the beginning of the experiment, but the rats pre-fed for 4 weeks could not recognize the EFA-containing diet. The non pre-fed animals continued to prefer the EFA-containing diet for about 2 weeks. From these results we could demonstrate that rats have a mechanism to distinguish the EFA in their diet, but this EFA selection ability was only in the early period of the experiment, and diminished soon after.