One hundred eighty-five patients hospitalized for evaluation to thrive were reviewed retrospectively. Eighteen percent had proven organic etiologies. The specific organic diagnosis was strongly suggested by the history and physical examination in all of these patients. Fifty percent of the patients were failing to thrive on the basis of environmental deprivation. Only 1.4% of the laboratory studies performed were of positive diagnostic assistance. No study was of positive value without a specific indication from the clinical evaluation. The history and physical examination are the most valuable tools in the evaluation of failure to thrive. Laboratory investigations are rarely helpful without a specific indication from the clinical evaluation.