Thirteen patients with severe chronic aortic regurgitation (mean age 52.5 years) were studied by serial M-mode echocardiography. When first studied, none had breathlessness caused by left ventricular failure (LVF). Nine of these patients remained asymptomatic over a mean period of 4 years, 3 months (no LVF group); the other four patients developed left ventricular failure with dyspnea after a mean interval of 3 years, 11 months (LVF group). For both of these groups, we compared the echocardiographic measurements from the first and last of the serial studies. For the LVF group, end-diastolic left ventricular internal dimension increased 14%, end-systolic dimension increased 35%, fractional shortening decreased 45% and left atrial dimension increased 62%. All of these changes were significant. For the No LVF group, the change in end-diastolic left ventricular internal dimension was not significant, but the 6% increase in end-systolic dimension, 10% reduction in fractional shortening and 25% increase in left atrial size were all statistically significant. Although echocardiography could detect declining left ventricular function in a group of asymptomatic patients with severe chronic aortic regurgitation, the reproducibility of the technique was limited in individual patients. Therefore, serial echocardiographic studies should be interpreted in conjunction with clinical assessment and other investigations.