Sixty-eight bottle-fed babies under 9 months of age with mild acute gastroenteritis were observed to evaluate current feeding regimens following acute gastroenteritis in infancy. All babies were fed for 24 h with a glucose-electrolyte mixture (GEM) and then randomly milk, i.e., slow regrade; immediate return to full-strength formula; or a rapid degrade to a hypoallergenic whey hydrolysate formula. All groups were well matched for age, sex, ethnic origin, nutritional state, and degree of hydration. There was no significance difference in stool frequency or reducing substances, vomiting, and duration of hospital stay between the three groups. Many infants (6/24) refused to take the whey hydrolysate formula, presumably because of unpalatability. Weight gain was more rapid when full-strength milk ws given. Clinical relapse developed in 12 (17%) of patients. An enteric pathogen was detected in eight of this group and cow''s milk protein intolerance in three (one from each feeding group). No infant had clinically significant lactose intolerance, in marked contrast to previous experienced at Queen Elizabeth Hospital. In this group of previously healthy, well-nourished babies with mild acute gastroenteritis, there was no advantage in regarding slowly to milk or a hypoallergenic formula. An immediate return to normal formula 24 h after GEM feeding was well tolerated and simpler for parents.