The effects of quiet respiration on assessment of left ventricular function by two-dimensional echocardiography were investigated in 12 healthy men. End-diastolic area in the parasternal short-axis view decreased with inspiration (from 17.3 +/- 2.1 [mean +/- SD] to 16.0 +/- 2.1 cm2, p less than .01), while end-systolic area did not change (from 7.6 +/- 1.4 to 7.7 +/- 1.5 cm2; NS). A fixed cursor that was located through the center of the left ventricular area at end-expiration made a tangential cut of the area at end-inspiration were smaller along the cursor than through the center of the short-axis area both at end-diastole (1.9 +/- 1.7 mm; p less than .01) and end-systole (3.8 +/- 4.0 mm; p less than .01). Our results suggest a need for standardization with regard to respiratory phases in assessment of left ventricular function by two-dimensional echocardiography and indicate the occurrence of inspiratory reduction of left ventricular stroke volume associated with decreased diastolic filling. Motion of the heart relative to the echo beam may play a part in the respiratory variations in left ventricular dimensions assessed by M mode echocardiography.