Two-dimensional transthoracic echocardiography has been shown to be a reliable and accurate method of measuring stenotic mitral valve orifice area. Little data exist on the role of two-dimensional transesophageal echocardiography for this purpose. Thus in 45 adult patients with mitral stenosis mitral valve area was determined by direct planimetry with the use of two-dimensional transesophageal and transthoracic echocardiography. Transesophageal was less feasible than transthoracic echocardiography in the 45 patients (69% vs. 89%, p < 0.025). In 14 patients, two-dimensional transesophageal echocardiography was not feasible, primarily because of leaflet dropout. In 30 patients, transesophageal and transthoracic echocardiography were feasible, and measurements of mitral valve area by the two techniques correlated well (r = 0.91, SEE = 0.33 cm2, p < 0.0001). Mean mitral valve orifice area determined by transesophageal echocardiography (1.54 +/- 0.75 cm2; range 0.56 to 3.49 cm2) and by transthoracic echocardiography (1.55 +/- 0.78 cm2; range 0.62 to 3.68 cm2) did not differ (p = NS). The absolute (0.24 +/- 0.22 cm2) and percent (19% +/- 21%) differences between mitral valve area determined by transesophageal versus transthoracic echocardiography were small. These data show that mitral valve area in patients with mitral stenosis can be accurately measured by direct planimetry with two-dimensional transesophageal echocardiography. Technical refinements such as lateral-gain-compensation features may improve the feasibility of two-dimensional transesophageal echocardiography for measurements of mitral stenosis area, and this technique may become an adjunct to transthoracic echocardiography in the assessment of severity of mitral stenosis.