A large left atrial (LA) V wave can be observed in patients with pure mitral stenosis (MS) due to decreased LA compliance. Based on the hypothesis that exercise capacity may correlate with the magnitude of the LA V wave in patients with MS, symptom-limited exercise testing and right and left heart catheterization were performed in 28 patients. The results show that the magnitude of the LA V wave (p = 0.02) was the strongest predictor of the exercise duration, suggesting that LA compliance may be an important contributing factor in determination of exercise capacity in patients with MS.