In this study, niacin was added to existing therapy for 3 months in 54 subjects with stable coronary artery disease. Average total cholesterol, low-density lipoprotein (LDL), high-density lipoprotein (HDL), and triglyceride levels were similar between groups. Three months of niacin treatment increased total HDL by 7.5% and decreased triglycerides by 15% compared with baseline values (p <0.005 for each), whereas total cholesterol and LDL levels remained unchanged. Addition of niacin resulted in a 32% increase in large-particle HDL (p <0.001), an 8% decrease in small-particle HDL (p = 0.0032), an 82% increase in large-particle LDL (p = 0.09), and a 12% decrease in small-particle LDL (p = 0.008). Niacin decreased lipoprotein-associated phospholipase A2 and C-reactive protein levels (20% and 15%, respectively, p <0.05 for the 2 comparisons). No significant changes from baseline were seen in any tested parameter in subjects who received placebo. In conclusion, addition of niacin to existing medical regimens for patients with coronary artery disease and already well-controlled LDL levels favorably improves the distribution of lipoprotein particle sizes and inflammatory markers in a manner that would be expected to confer atheroprotection. The effect of altering lipoprotein particle distribution and inflammatory markers on surrogate markers of atherosclerosis and clinical cardiovascular events in this population remains unclear.