Although the pathophysiology of persistent diarrhea in children remains unclear, it has been suggested that it may be related to the composition of the food ingested. Since lactase deficiency and cow's milk protein intolerance are often identified in children with persistent diarrhea, replacement of milk with yogurt should be beneficial. We, therefore, compared the clinical outcome of children (aged 3-36 months) with persistent diarrhea randomly assigned to receive either milk or yogurt for 5 days. Preliminary results on 45 of the 100 children indicated clinical failure, which was determined after a 5% loss of body weight per day or the persistence of diarrhea after 5 days, in only 14% of the children fed yogurt compared to 42% of those fed milk (p less than 0.05). These preliminary results strongly suggest a clinical advantage of feeding yogurt rather than milk in children with persistent diarrhea.