OBJECTIVE: We sought to evaluate the effects of muraglitazar, a dual (alpha/gamma) peroxisome proliferator-activated receptor (PPAR) activator within the new glitazar class, on hyperglycemia and lipid abnormalities. RESEARCH DESIGN AND METHODS: A double-blind, randomized, controlled trial was performed in 1,159 patients with type 2 diabetes inadequately controlled with metformin. Patients received once-daily doses of either 5 mg muraglitazar or 30 mg pioglitazone for a total of 24 weeks in addition to open-label metformin. Patients were continued in a double-blind fashion for an additional 26 weeks. RESULTS: Analyses were conducted at week 24 for HbA1c (A1C) and at week 12 for lipid parameters. Mean A1C at baseline was 8.12 and 8.13% in muraglitazar and pioglitazone groups, respectively. At week 24, muraglitazar reduced mean A1C to 6.98% (-1.14% from baseline), and pioglitazone reduced mean A1C to 7.28% (-0.85% from baseline; P < 0.0001, muraglitazar vs. pioglitazone). At week 12, muraglitazar and pioglitazone reduced mean plasma triglyceride (-28 vs. -14%), apolipoprotein B (-12 vs. -6%), and non-HDL cholesterol (-6 vs. -1%) and increased HDL cholesterol (19 vs. 14%), respectively (P < 0.0001 vs. pioglitazone for all comparisons). At week 24, weight gain (1.4 and 0.6 kg, respectively) and edema (9.2 and 7.2%, respectively) were observed in the muraglitazar and pioglitazone groups; at week 50, weight gain and edema were 2.5 and 1.5 kg, respectively, and 11.8 and 8.9%, respectively. At week 50, heart failure was reported in seven patients (five with muraglitazar and two with pioglitazone), and seven deaths occurred: three from sudden death, two from cerebrovascular accident, and one from pancreatic cancer in the muraglitazar group and one from perforated duodenal ulcer in the pioglitazone group. CONCLUSIONS: We found that 5 mg muraglitazar resulted in greater improvements in A1C and lipid parameters than a submaximal dose of 30 mg pioglitazone when added to metformin. Weight gain and edema were more common when muraglitazar was compared with a submaximal dose of pioglitazone.