The effects of a 13 wk moderate exercise program on fasting plasma insulin, lipids and lipoprotein cholesterol concentrations were studied in 32 sedentary, middle-aged men with coronary artery disease. The preponderant component of the exercise program was walking or slow jogging. There was no significant change in the systolic blood pressure and pulse rate product response to a standard exercise load. The high-density lipoprotein-cholesterol (HDL-C) level increased and the fasting plasma insulin concentration decreased. There were no significant changes in plasma triglycerides or low-density lipoprotein cholesterol levels. In sedentary subjects with coronary artery disease a modest increase in activity can result in an increase in the HDL-C level and a decrease in the plasma insulin concentration. These changes occurred in the absence of variations in diet, smoking habits, adiposity or plasma triglyceride concentrations and did not require a cardiovascular training effect.