Background:At present,China has listed the compound tablet containing a fixed dose ofrosiglitazone and metformin,Avandamet,which may improve patient compliance.The aim of this study was to evaluate the efficacy and safety of Avandamet or uptitrated metformin treatment in patients with type 2 diabetes inadequately controlled with metformin alone.Methods:This study was a 48-week,multicenter,randomized,open-labeled,active-controlled trial.Patients with inadequate glycaemic control (glycated hemoglobin [HbA1c] 7.5-9.5％) receiving a stable dose of metformin (≥1500 mg) were recruited from 21 centers in China (from 19 November,2009 to 15 March,2011).The primary objective was to compare the proportion of patients who reached the target of HbA1c ≤7％ between Avandamet and metformin treatment.Results:At week 48,83.33％ of patients reached the target of HbA 1 c ≤7％ in Avandamet treatment and 70.00％ in uptitrated metformin treatment,with significantly difference between groups.The target of HbAlc ≤6.5％ was reached in 66.03％ of patients in Avandamet treatment and 46.88％ in uptitrated metformin treatment.The target of fasting plasma glucose (FPG) ≤6.1 mmol/L was reached in 26.97％ of patients in Avandamet treatment and 19.33％ in uptitrated metformin treatment.The target of FPG ≤7.0 mmol/L was reached in 63.16％ of patients in Avandamet treatment and 43.33％ in uptitrated metformin treatment.Fasting insulin decreased 3.24 ± 0.98 μU/ml from baseline in Avandamet treatment and 0.72 ± 1.10 μU/ml in uptitrated metformin treatment.Overall adverse event (AE) rates and serious AE rates were similar between groups.Hypoglycaemia occurred rarely in both groups.Conclusions:Compared with uptitrated metformin,Avandamet treatment provided significant improvements in key parameters ofglycemic control and was generally well tolerated.Registration number:ChiCTR-TRC-13003776.