AbstractWe examined M‐mode echocardiograms on 35 patients with catheterization‐proven mitral stenosis and normal sinus rhythm to determine whether the presence or absence of an A wave on the mitral echogram predicted mild versus severe mitral stenosis. Mitral valve area (MVA) was determined by the Gorlin formula. Presence of a mitral A wave was defined as 2 mm or greater anterior motion (after a well‐defined F point) of the anterior mitral leaflet. In six of 35 patients, the presence of an A wave was equivocal. Of the remaining 29 patients, 16 had no A wave and mean MVA = 1.18 cm2 ± 0.45 (SD), and 13 patients had a definite A wave and mean MVA = 2.04 cm2 ± 0.71. There was a significant difference (p < 0.001) between the mean MVA for patients with and without definite A waves. No patients with a definite A wave had an MVA less than 1.2 cm2. An A wave on the mitral echogram (in sinus rhythm) excludes severe mitral stenosis; when an A wave is not seen, no definite statement concerning severity of mitral stenosis can be made.