['The purpose of this research was to compare the effects of niacin extended-release in combination with simvastatin (NER/S) versus atorvastatin monotherapy on high-density lipoprotein (HDL) particle number and size in patients with hyperlipidemia or dyslipidemia from the SUPREME study.', 'This was a post hoc analysis of patients (n = 137) who completed the SUPREME study and who had lipid particle number and size measurements at both baseline and at week 12 by nuclear magnetic resonance spectroscopy. Following ≥4 weeks without lipid-modifying therapy (washout period), the patients received NER/S 1000/40 mg/day for 4 weeks followed by NER/S 2000/40 mg/day for 8 weeks, or atorvastatin 40 mg/day for 12 weeks. Median percent changes in HDL particle number and size from baseline to week 12 were compared between the NER/S and atorvastatin treatment groups using the Wilcoxon rank-sum test. Distribution of HDL particle subclasses at week 12 was compared between the treatment groups using the Cochran-Mantel-Haenszel test.', 'Treatment with NER/S resulted in a significantly greater percent reduction in small HDL particle number at week 12 compared with atorvastatin monotherapy (-1.8% versus 4.2%, P = 0.014), and a numerically greater percent increase in large HDL particle number (102.4% versus 39.2%, P = 0.078) compared with atorvastatin monotherapy. A significantly greater percent increase in HDL particle size from baseline at week 12 was observed with NER/S compared with atorvastatin (6.0% versus 1.3%, P < 0.001). NER/S treatment also resulted in a significant shift in HDL particle size from small and medium at baseline to large at week 12 (P < 0.0001).'] Does niacin extended-release/simvastatin combination therapy produce larger favorable changes in high-density lipoprotein particles than atorvastatin monotherapy?