We evaluated left ventricular (LV) mechanical efficiency in 23 elderly patients (mean age 67 +/- 2) with coronary artery disease (CAD) and in 22 patients younger than 65 years (mean age 49 +/- 8) with similar severity of CAD (2.4 +/- 0.8 and 2.2 +/- 0.8 vessels per patient, respectively) and history of myocardial infarction (34% and 41%, respectively). LV mechanical efficiency was calculated as the ratio of LV work per minute and myocardial O2 consumption. LV stroke volume was calculated from left ventriculography. Coronary blood flow was measured by thermodilution. Older patients had lower values of LV stroke volume (49 +/- 16 vs 73 +/- 16 mL, p < 0.005), ejection fraction (41 +/- 17 vs 58 +/- 17%, p < 0.05), LV stroke work (93 +/- 26 vs 131 +/- 41 g.m., p < 0.02) and LV work per minute (6.7 +/- 2.6 vs 9.3 +/- 2.7 kg.m./min, p < 0.05). Since myocardial O2 consumption was similar in the two groups, LV mechanical efficiency was lower in older CAD patients (16.2 +/- 15 vs 23.8 +/- 12%, p < 0.05). Thus, elderly patients with CAD show a reduced LV mechanical pump performance and efficiency, compared with younger patients with similar disease severity and history of myocardial infarction. These observations may contribute to understanding the higher frequency of congestive heart failure in elderly patients with CAD.