The common acute and chronic illnesses that may influence a youths' participation in sports are discussed. Conditions dis cussed include fever, upper and lower respiratory infection, infectious mononucleosis, and dermatoses (viral, fungal, bac terial and parasitic, and traumatic). The chronic diseases pre sented include asthma, epilepsy, diabetes, and cardiovascular problems, especially congenital and rheumatic lesions as well as arrhythmias and hypertension. The cardiovascular evalua tion of the young athlete is detailed because, along with the orthopaedic examination, it probably is the area to yield the most abnormal or questionable findings.