The aim of the study was to investigate whether a fatiguing exercise on treadmill affects balance performance in recreationally active men and women. Nineteen subjects, aged 18-26 years, were assessed before and after a fatiguing exercise, using the Balance Error Scoring System (BESS). Fatiguing exercise was performed on treadmill using the Bruce protocol. A significant effect of fatigue was present in men (P < 0.05) and women (P < 0.05). Women performed at a significantly lower total BESS scores than men at both pretest (P < 0.05) and posttest (P < 0.05). The mean difference (posttest-pretest) between men and women was not significant (P > 0.05). These findings suggest that a fatiguing exercise induced by means of treadmill increases postural sway in healthy subjects, and that this increase in postural sway is sex-independent. © 2009 - IOS Press and the authors. All rights reserved.