OBJECTIVE To evaluate erythrocyte deformability, nitric oxide metabolites, and their modifications induced by exercise in athletes who practised different sports. METHODS This evaluation was effected before and after cardiopulmonary test, using a cycloergometer. METHODS The study was performed in the Department of Internal Medicine, Cardiovascular and Renal Diseases of the University of Palermo. METHODS We enrolled 62 male athletes who practised endurance (n = 23), mixed (n = 20), and power (n = 19) sports and 20 sedentary male subjects as controls. METHODS No subject had diabetes or hypertension or dyslipidemia. Five control subjects and 14 athletes were smokers. METHODS Erythrocyte deformability was examined as elongation index (EI) using a diffractometer. The nitric oxide metabolites (nitrite + nitrate = NOx) were evaluated employing the Griess reagent. RESULTS In the whole group, an increase in EI and NOx was present. Subdividing the whole group into 3 subgroups, we noted an increase in EI and NOx only in endurance and mixed athletes. The EI before and after the cardiopulmonary test significantly decreased in the whole group and in power athletes but not in endurance and mixed athletes. Before and after the test, NOx did not significantly change in the whole group and in the 3 subgroups. CONCLUSIONS In athletes who practised endurance and mixed sports, we observed an increase of NOx level and an increase of erythrocyte deformability. The latter did not change after an exercise test in the same subgroups, whereas it decreased in power athletes.