Upper respiratory illness may cause more disability among athletes than all other diseases combined. This paper presents the essential epidemiology, risks of infection, and transmission features of upper respiratory illness. Those who provide health care for athletes must understand the subsequent implications of an upper respiratory illness on sport performance and should be familiar with participation and clinical management guidelines for athletes with an upper respiratory illness. The literature suggests that regular, rigorous exercise increases both the incidence and severity of upper respiratory illness, yet the immune system appears to have a distinct level at which moderate exercise promotes optimum health. Although research indicates that upper respiratory illness infections are surprisingly reluctant transmitters, upper respiratory illness transmission may escalate during winter sports seasons. The impact of upper respiratory illness on selected pulmonary, cardiac, and skeletal muscle functions may lead to illness complications in athletes, and sport performance during illness may also decline. Athletes should monitor symptoms, adjust training schedules, and rest during an upper respiratory illness.