Seventy-seven patients undergoing elective cardiac catheterization were administered a diagnostic psychiatric interview and their mean heart rates and heart rate variability were determined from the results of a 24 hr ambulatory ECG. The mean heart rate for depressed patients with coronary artery disease (CAD) was significantly higher than for nondepressed CAD patients, independent of the patient's age, smoking status, and beta blocker therapy. Heart rate variability was lower in depressed patients but did not achieve significance. With the exception of smoking, which was more common in depressed patients, there were no significant differences between the depressed and nondepressed patients on any other medical or demographic variable assessed. It is concluded that elevated heart rate may represent increased sympathetic tone in depressed CAD patients, and may help to explain the increased morbidity and mortality reported in these patients.