P-wave dispersion (PWD) is a new electrocardio-graphic marker that has been associated with inhomogeneous and discontinuous propagation of sinus impulses.(1,2) It can be defined as the difference between maximum and minimum P-wave duration. The prolongation of intra-atrial and interatrial conduction time, and the inhomogeneous propagation of sinus impulses are well known electrophysiologic characteristics of the atrium prone to fibrillate. (1,2) Furthermore, prolonged P-wave duration and increased PWD have been reported to carry an increased risk for atrial fibrillation (AF).(2,3) reurnatic mitral stenosis (MS) is frequently seen in developing countries and causes significant morbidity and mortality.(4) Percutaneous mitral balloon valvuloplasty (PMBV) is the procedure of choice in patients who have symptomatic, hemodynamically severe MS, and are suitable for this procedure.(4-6) . This procedure is highly successful with a low complication rate and significant short- and long-term improvement in hemodynamics and symptoms.(7,8). 8 The objectives of this study were (1) to identify PWD in patients with MS, and (2) to determine the effects of PMBV on PWD. There is currently no study on the effects of MS and PMBV on PWD.