Background: To evaluate the safety and effectiveness of rosiglitazone/metformin in patients with type 2 (non-insulin-dependent) diabetes Methods: A total of 982 patients were enrolled by 19 physicians from November 2003 to November 2010. Patients treated with rosiglitazone/metformin at least once, were included in safety assessment. The incidences of adverse events (AEs) and serious adverse events (SAEs) were estimated. The effectiveness of rosiglitazone/metformin was evaluated through change in fasting blood glucose (FBG), 2-hour postprandial glucose (2hr PPG), Hemoglobin A1c (HbA1c). Results: Of the 982 patients, 713 patients with the mean age of $56.4{pm}11.5$ years were included in the safety assessment. A total of 130 AEs were reported from 110 patients (15.4 %). The most frequent AEs were upper respiratory infection (2.4 %), oedema (2.2 %), gastritis (1.3 %), and weight increase (1.1 %). The incidence of unexpected AEs was 5.9 % (42/713, 47 AEs). Three SAEs such as bacterial pneumonia, hyperglycaemia, chest pain were reported in 2 patients. As it is about effectiveness, patients showed statistically significant reductions after treatment of rosiglitazone/metformin in FBG, 2hr PPG, and HbA1c (P<0.001 by paired t-test, for all). Conclusion: Our data suggest that rosiglitazone/metformin is well tolerated and effective in Korean patients with type 2 (non-insulin-dependent) diabetes.