Failure to thrive (FTT) is a common problem that occurs when caloric intake is insufficient to maintain growth. For the majority of children it can be reversed with behavioral modifications and increased caloric provisions. In a minority of cases, FTT is the symptom of underlying organic disease. Routine evaluation with laboratory tests, imagining studies, and endoscopy results in an etiology of FTT in <1.4% of cases, and when investigations are positive the organic etiology is most often suspected based on history and/or physical examination. Therefore, these evaluations should be limited to those children with clear symptoms of organic disease and those who fail to grow with behavioral and nutritional interventions.