In 65 patients examined by mechanical sector and M-mode echocardiography, left ventricular volumes and ejection fraction were determined. Comparison with biplane ventriculography has shown that the above-mentioned parameters can be determined by sector relatively very reliably. Correlation coefficients for end-diastolic and end-systolic volumes were 0.74 and 0.85 respectively, for the ejection fraction 0.78. Substantially less close correlations were found for parameters obtained by one-dimensional echocardiography, especially in patients with segmental disturbances of kinetics and abnormal left ventricular geometry. The greatest contribution of this laborious and demanding method consists in the possibility of relatively reliable estimation of left ventricular volumes and ejection fraction by two-dimensional echocardiography also in these patients.