One of every six children in the United States is so weak, uncoordinated, or generally inept that he or she is physically underdeveloped by the standards of the President's Council on Physical Fitness and Sports. This booklet outlines diagnostic tests that can identify physical difficulties or shortcomings in children between the ages of 9 to 17 years. Observation techniques are described, and means of improving performance and developing better physical development are discussed. (JD)