The authors evaluated physiologic, psychologic and metabolic effects of a nine-week in-hospital training program on 14 men with severe disabling angina pectoris. The exercise program consisted of intensive interval training on an ergometer bicycle for two 30 min sessions daily. The physical performance increased by about 40% (p less than 0.001). Plasma insulin levels were reduced and glucose tolerance improved significantly. There was a decrease in plasma triglyceride and low-density lipoprotein (LDL) cholesterol levels, but no change in high-density lipoprotein (HDL) cholesterol, apolipoprotein AI and B concentrations. Plasma triglyceride (p less than 0.05) and LDL cholesterol (p less than 0.05) levels remained low three weeks after completion of the training period and the physical performance remained improved (p less than 0.01) even six months post-training. Four of the patients who had been disabled for at least five months were able to return to work. The authors suggest that comparatively short and intensive in-hospital rehabilitation of patients with coronary heart disease may be an attractive alternative to prolonged training on an outpatient basis, especially in patients with severe angina pectoris.