Previous determinations of normal valve orifice areas have been mainly from postmortem studies. In this study mitral and aortic valve orifice area were determined from two dimensional echocardiograms in 20 normal subjects and 20 patients with congestive cardiomyopathy. Mitral valve orifice area was larger than quoted in standard textbooks. Both mitral and aortic valve orifice area were reduced in patients with cardiomyopathy. Valve opening was assessed relative to left ventricular and aortic root size. The ratio of mitral valve orifice area to left ventricular cross-sectional area was markedly reduced in patients with cardiomyopathy compared with normal subjects. The ratio of aortic valve orifice area to aortic root size also was reduced in patients with cardiomyopathy. Anterior mitral leaflet E point-septal separation was similar to that in previous reports contrasting normal subjects with patients with myopathy. Among patients with cardiomyopathy, mitral E point-septal separation was primarily a function of left ventricular size and was not significantly correlated with fractional shortening or ejection fraction within this group having uniformly poor systolic function.