Ethanol administered to weanling rats in various concentrations as the sole drinking fluid in conjunction with a semipurified dry diet was consumed at a level of not more than 20% of total energy. Suppression of fluid intake and concomitant reduction of food intake resulted in decreased growth. Analysis of body composition indicated that the difference in weight in rats given 20% solutions of ethanol as the sole drinking fluid and in rats pair-fed diets without ethanol was primarily due to dehydration. With total liquid formulations having good resistance to separation, there were no significant differences in weight gain between rats given 20% or 30% of total energy as ethanol and rats pair-fed diets without ethanol. Ethanol fed at 40% of total energy caused inhibition of growth which could not be ascribed solely to decreased consumption of food and water. These data indicate that the method of administering ethanol to weanling rats affects not only the levels at which ethanol is toxic but also the amount of ethanol voluntarily consumed by the rats. The use of pair-feeding techniques and of homogenous liquid formulations is essential for studies of the metabolic effects of ethanol.