Patients with type IIb, or mixed, dyslipidemia have high levels of low-density lipoprotein cholesterol (LDL-C) with predominance of small dense LDL particles, high levels of triglycerides (TG), and low levels of high-density lipoprotein cholesterol (HDL-C). Fenofibrate significantly reduces TG and, more moderately, LDL-C, increases HDL-C and produces a shift from small to large LDL particle size; the main effect of ezetimibe is a reduction in LDL-C levels. Combined treatment with fenofibrate and ezetimibe may correct all the abnormalities of type IIb dyslipidemia. To assess the efficacy and safety of coadministration of fenofibrate (NanoCrystal(R)) and ezetimibe in patients with type IIb dyslipidemia and the metabolic syndrome compared with administration of fenofibrate and ezetimibe alone (ClinicalTrials.gov Identifier: NCT00349284; Study ID: CLF178P 04 01). This was a prospective, randomized, double-blind, three-parallel arm, multicenter, comparative study. Sixty ambulatory patients (mean age 56 years; 50% women, 50% men) were treated in each group. For inclusion in the study, patients were required to have LDL-C >or=4.13 mmol/L (>or=160 mg/dL), TG >or=1.71 mmol/L and <or=4.57 mmol/L (>or=150 mg/dL and <or=405 mg/dL), and at least two of the following National Cholesterol Education Program Adult Treatment Panel III criteria for the metabolic syndrome: low HDL-C or increased fasting plasma glucose, blood pressure, or waist circumference. Patients received fenofibrate 145 mg, ezetimibe 10 mg, or coadministration of both (fenofibrate/ezetimibe) daily for 12 weeks. The outcome measures were changes in lipids and related parameters, apolipoproteins, glucose metabolism parameters, and high-sensitivity C-reactive protein (hsCRP). Fenofibrate/ezetimibe was more effective than either fenofibrate or ezetimibe in reducing LDL-C (-36.2% vs -22.4% and -22.8%, respectively), non-HDL-C (-36.2% vs -24.8% and -20.9%, respectively), total cholesterol (TC) [-27.9% vs -18.9% and -17.1%, respectively], apolipoprotein B (-33.3% vs -24.5% and -18.7%, respectively), TC/HDL-C ratio (-34.2% vs -23.0% and -17.0%, respectively), and apolipoprotein B/apolipoprotein AI ratio (-37.5% vs -27.0% and -17.7%, respectively) [p < 0.001 for all comparisons between fenofibrate/ezetimibe and monotherapies]. Fenofibrate/ezetimibe was as effective as fenofibrate and more effective than ezetimibe in reducing remnant-like particle cholesterol (-36.2% and -30.7% vs -17.3%, respectively), and in increasing LDL size (+2.1% and +1.9% vs + 0.7%, respectively), apolipoprotein AI (+7.9% and +5.1% vs +0.2%, respectively) and apolipoprotein AII (+24.2% and +21.2% vs +2.7%, respectively). Fenofibrate/ezetimibe and fenofibrate were equally effective in reducing TG (both -38.3%) and in increasing HDL-C (+11.5% and + 7.9%, respectively; p = 0.282). Ezetimibe had minor effects on TG (-10.4%) and HDL-C (+2.2%). Among patients with low HDL-C at baseline (<1.29 mmol/L [<50 mg/dL] in women, <1.03 mmol/L [<40 mg/dL] in men), normalization of HDL-C was observed in 52.9% with fenofibrate/ezetimibe and in 58.8% with fenofibrate, compared with 20.0% with ezetimibe. Changes in hsCRP were -25.9% with fenofibrate/ezetimibe, -27.8% with fenofibrate, and -10.2% with ezetimibe (not statistically significant). None of the treatments altered glucose metabolism parameters. In patients with type IIb dyslipidemia and features of the metabolic syndrome, coadministration of fenofibrate 145 mg and ezetimibe 10 mg daily was more effective than either monotherapy in reducing LDL-C, non-HDL-C, apolipoprotein B, and cardiovascular risk ratios, and was as effective as fenofibrate 145 mg alone in reducing TG and in increasing HDL-C in patients with low baseline HDL-C levels.