The efficacy and safety of tesaglitazar (0.5 and 1 mg) and pioglitazone (15, 30 and 45 mg) were compared in a 24-week, randomised, double-blind study in 1,707 patients with type 2 diabetes mellitus. Tesaglitazar 1 mg was non-inferior to pioglitazone 45 mg for change from baseline in glycosylated haemoglobin (HbA1C) at 24 weeks (difference: -0.056 [95% confidence intervals -0.161, 0.049], pNI<0.001 for non-inferiority hypothesis). Tesaglitazar 1 mg improved triglyceride (TG), high-density lipoprotein cholesterol (HDL-C) and non-HDL-C levels compared with all pioglitazone doses at 24 weeks (p<0.001). Low-density lipoprotein cholesterol (LDL-C) was lower with tesaglitazar for all pioglitazone comparisons (p<0.05), except for tesaglitazar 0.5 mg versus pioglitazone 15 mg. Tesaglitazar 1 mg decreased LDL particle number, when compared with all pioglitazone doses (p<0.01). Both agents increased body weight and peripheral oedema in a dose-dependent manner, but only tesaglitazar increased serum creatinine. In summary, tesaglitazar provided similar glycaemic control to pioglitazone, was associated with significant improvement in lipid and lipoprotein variables, and increased serum creatinine in a dose-dependent manner.