Left atrial function was assessed by transesophageal echocardiography in 8 patients with mitral stenosis and sinus rhythm (MS group), and 16 age-matched normal controls (C group). Pulsed Doppler findings of left upper pulmonary vein flow were classified into first and second forward waves during systole (S1, S2), forward wave during diastole (D), and backward flow during left atrial contraction (PVA). Peak velocity (P) and time-velocity integral (TVI) of each wave and acceleration and deceleration slope of S2 wave (S2-Ac, S2-Dc) were obtained. TVI-S2 and P-D in the MS group were significantly lower than those in the C group (TVI-S2: 4 +/- 2 vs 12 +/- 3 cm, P-D: 27 +/- 13 vs 41 +/- 12 cm/sec). S2-Ac and S2-Dc in the MS group were significantly higher than those in the C group (S2-Ac: 456 +/- 116 vs 323 +/- 118 cm/sec2, S2-Dc: 380 +/- 102 vs 165 +/- 48- cm/sec2). There were no differences in S1 and PVA. Lower TVI-S2 in the MS group suggests decreased reservoir function of the left atrium. Lower TVI-S2 in the MS group was caused by increased S2-Ac and S2-Dc which suggests increased left atrial preload and deterioration of left atrial compliance. Decreased P-D in the MS group reflects dysfunction of mitral valve opening.