There is general agreement that chronic diarrhea due to cow's milk allergy (CMA) resolves with a cow's milk-free diet, and that tolerance to cow's milk is achieved by 2 years of life. We have followed for 4 to 10 years, 41 infants with chronic diarrhea due to CMA, who had at onset of diarrhea RAST and/or skin tests positive to cow's milk. After the diarrhea subsided, the diet was continued for 6 months and, subsequently, cow's milk reintroduction was attempted at 6-month intervals. In contrast to 25/37 children (four cases were lost to follow-up) in whom CMA subsided at a median age of 2 years, 12/37 (32.5%) children did not tolerate cow's milk at a median age of 6 years. In addition, a large proportion of children (27/37 = 73%) suffered during the follow-up period from other atopic manifestations, due either to CMA or to inhalant allergy. Our data suggest that in infants with chronic diarrhea due to CMA, RAST and/or skin tests positive to cow's milk may indicate either the tendency of CMA to persist throughout childhood, or the risk of developing other atopic diseases.