• We studied 16 children aged 18 months or less who had severe primary protein-calorie malnutrition. All were admitted to one urban pediatric teaching hospital for treatment of failure to thrive between Jan 1, 1980, and Aug 30, 1984. The definitions of malnutrition were based on those of the Wellcome Trust. The patients had no evidence of medical causes for their conditions and grew rapidly when they were refed in the hospital. Eight were products of teenage pregnancies. Eleven patients were receiving public aid, and four had no thirdparty coverage. All were markedly below the fifth percentile in weight for length; their mean percentage of expected weight for age was 0.55. The mean hospital stay was 18.5 days. Severe primary protein-calorie malnutrition does exist in the United States. Thorough nutritional evaluation in children with failure to thrive is indicated, and malnutrition should be a reportable condition in the United States.