BACKGROUND: Assessment of left ventricular function with conventional 2-dimensional echocardiography (2D echo) remains largely qualitative and subjective because the manual tracing of endocardial borders is laborious and tedious. An automatic border detection (ABD) echo has been recently developed that permits real-time measurements of chamber areas and cardiac function. METHODS: To determine usefulness of ABD echo, left ventricular cross-sectional areas were automatically measured from the parasternal short-axis image in 25 cases including 9 cardiac patients, and compared with those by off-line analysis of the conventional 2D echo image. RESULTS: In on-line ABD analysis, short axis end-diastolic area averaged 13.1+/-2.2cm2, end-systolic area 5.3+/-1.3cm2 and fractional area change 59.4+/-9.0% and off-line manual analysis yielded corresponding values of 14.7+/-2.5cm2, 6.2+/-1.3cm2, and 57.1+/-7.1%. The end-diastolic and end-systolic areas by both methods were significantly different, respectively. Left ventricular end-diastolic and end-systolic area and fractional area change obtained from ABD echo correlated significantly with those of off-line measurements(r=0.897, p<0.001 ; r=0.505, p<0.01 ; r=0.427, p<0.05). CONCLUSION: Thus, these facts suggest that ABD echo is useful for on-line continuous measurement of chamber areas and cardiac function.