Sport undoubtedly provides health benefits of physical activity. Nevertheless, great physical efforts of top sport can transiently, but also permanently increase the risk od disease of many organic systems. Professional athletes, especially in endurance sports, may develop some cardiac disease. It is important to differentiate between a sick heart in the athlete and physiological adjustments of the heart to sports activities, called athlete's heart. Lately, greater attention has been given to right ventricular remodelling in endurance sports. It can cause disorders of ventricular conduction, premature ventricular beats and potentially life-threatening arrrhythmias. Atrial fibrillation and atrial flutter are also more common in endurance sports and their pathophysiological mechanism is complex. Sudden cardiac death may be a consequence of great physical efforts of training and competing in predisposed athletes. Exercise-induced asthma and exercise-induced bronchoconstriction are clinical entities in which physical effort causes bronchal hyperreactivity. Diagnosis of this condition is based on signs and symptoms, spirometry findings and bronchal provocation tests. In some sports and sport disciplines, especially after retiring from professional sports, a greater prevalence of obesitiy, insulin resistance and metabolic syndrome has been observed. Those diseases are especially common in anaerobic exercises. Professional sports activity in women may lead to development of disorders of menstrual cycle, but also to development of female athlete triad. As a consequence of high level training and adjustment to sport mostly female athletes, but also some male athletes, may develop eating disorders. Runner's colitis is a relatively common adverse effect in long-distance runners, but also in other endurance sports and it can manifest with many symptoms, from flatulence to diarrhea and hematochezia. Hypoperfusion of gastrointestinal organs is considered to be the main etiological factor of this condition. Hypoperfusion, combined with some mechanical causes, causes problems in upper part od digestive system: gastroesophageal reflux, nausea, vomiting, gastritis, ulcers etc. Excessive physical exercise may casue exertional rhabdomyolisis. In the most severe cases it can result in kidney injury and kidney failure. It has been proved that top sports activity, especially in endurance sports, may cause iron deficiency, as well as iron deficiency anemia. Periods of high level training are considered to suppress iron absorption and the use of iron in erythropoiesis.