Objective We designed a multi-center, double-blind, randomized, parallel, with metformin controlled clinical trial to evaluate the efficacy and safety of low dose rosiglitazone combined with sulphonylurea therapy in type 2 diabetic patients who were inadequately controlled with sulphonylurea alone.Methods Patients were treated with 4 mg rosiglitazone once daily plus sulphonylurea (test group) or 0.5 g metformin twice daily plus sulphonylurea (control group) for 12 weeks. The mean levels of HbA1c, fasting and postprandial plasma glucose were recorded and compared between the two groups.Results The mean levels of HbA1c decreased by 1.09% and 0.95% in the test group (n=102) and control group (n=96) respectively. Fasting and postprandial plasma glucose levels in the test group decreased by 25.0% and 35.6%, and in the control group, decreased by 17.7% and 23.8% as compared with the baseline (both P