FAILURE TO THRIVE has become a popular term to describe infants and children whose growth and often development are significantly below expected standards. A review of admission diagnoses for the infant ward of the Yale-New Haven Hospital during one year showed an average of two infants a month admitted with a diagnosis of failure to thrive or unexplained vomiting or feeding difficulties associated with poor growth. A few had a physical abnormality, which could reasonably explain impaired growth and nutrition. However, in many infants no organic basis was found after careful diagnostic appraisal. This outcome was frustrating to both the parents and the physician. Negative results could not completely resolve their fears of some undetected serious abnormality. Parents' feelings of guilt about their own contribution to the poor thriving of their infant were not helped. Without consideration of psychologic and social factors, it is often concluded that such a child