Failure to thrive is a syndrome of infancy and early childhood, characterized by growth failure for no apparent cause. A careful history, thorough physical examination, and relatively simple laboratory and radiographic studies will identify the cause of the problem in most instances. Prenatal, genetic, familial, constitutional, and environmental factors are most important. Hospitalization for diagnostic evaluation is often effective from a therapeutic standpoint as well. The family physician is in a favorable position to manage most pediatric patients who fail to thrive.