In this study, 113 patients with modestly elevated levels of low-density lipoprotein cholesterol (<210 mg/dl) and coronary artery disease were randomized to an intervention group (n=56) or a control group (n=57). The intervention program consisted of daily exercise and a low-fat diet according to the American Heart Association's recommendation phase III; patients in the control group received "usual care" rendered by their private physician. After 1 year, complete data were available for all 92 patients (intervention: n=40; control: n=52) who underwent repeat coronary angiography. During the study course, patients in the intervention group showed an increase in apolipoprotein A-I(123 +/- 18 vs 129 +/- 20 mg/dl; p < 0.02) and apolipoprotein A-I/B (1.3 +/- 0.4 vs 1.5 +/- 0.4; p <0.01) and a decrease in apolipoprotein B (99 +/- 20 vs 89 +/- 18 mg/dl; p < 0.01), while apolipoprotein A-II remained unchanged (38 +/- 6 vs 38 +/- 6 mg/dl; p=NS). In the control group, there were no significant changes (apolipoprotein A-I, 124 +/- 17 vs 128 +/- 13 mg/dl; apolipoprotein A-II, 38 +/- 6 vs 39 +/- 6 mg/dl; apolipoprotein B, 100 +/- 21 vs 99 +/- 16 mg/dl; apolipoprotein A-I/B, 1.3 +/- 0.3 vs 1.4 +/- 0.5; all p=NS). As previously reported, there was a significant retardation of progression in patients in the intervention group (progression 23%, no change 45%, regression 32%) compared with the control group (progression 48%, no change 35%, regression 17%) (p < 0.05). Although retardation of progression was significantly associated with an increase in apolipoprotein A-I/B and a decrease in apolipoprotein B (p < 0.05), these gave way in multivariate analysis to changes in total cholesterol/high-density lipoprotein cholesterol, absolute levels of low-density lipoprotein cholesterol, and, in a subgroup of patients, to leisure-time physical activity (all p < 0.05). These data demonstrate that an intervention based on a low-fat diet and intensive physical exercise is capable of improving apolipoprotein levels, associated with retardation of progression of coronary artery disease. However, total cholesterol/high-density lipoprotein cholesterol and low-density lipoprotein cholesterol appear superior to apolipoproteins as metabolic markers for effective treatment in patients with coronary artery disease.