Sixty-eight cases of chronic diarrhea in infancy over a 5-year period have been analysed with particular reference to differential diagnosis and management. A diagnosis was established in 63, the most common diagnoses being lactose intolerance (30.9%) and milk allergy (26.5%). Other diagnoses included intestinal lymphangiectasia, short bowel syndrome, Salmonella enteritis, inflammatory bowel disease, congenital chloridorrhea, adrenogenital syndrome, and ganglioneuroma. A systematic diagnostic approach for such specific disease entities was presented. Despite intensive investigation a diagnosis could not be established in 5 (7.3%) infants. For differential diagnosis and treatment, we observed the responses to fasting and change of formula. 54 (79.4%) of the infants responded to more than 24 hours of fasting, 48 (88.9%) of whom showed good responses to the changes of formula. The age of onset of diarrhea, body weight on admission, and laboratory findings did not influence the outcome of infants with chronic diarrhea, but only the interval period from onset to diagnosis did influence it.