The newly developed insulin sensitizer-thiazolidinediones have the potential to downregulate inflammation and autoimmune response. The objective of this study was to observe the beneficial effects on beta-cell function in the LADA patients treated with rosiglitazone. 54 LADA patients were assigned to oral hypoglycemic agents group (GAD-Ab<175 U/mL and FCP>0.3 nmol/L) or early insulin administration group (GAD-Ab>or=175 U/mL or GAD-Ab<175 U/mL and FCP<or=0.3 nmol/L). Then, those patients were randomly assigned to receive sulfonylureas (SUs group) or rosiglitazone (RSG group) therapy, or to receive insulin alone (INS group) or rosiglitazone plus insulin (INS+RSG group). Plasma glucose, HbA1c, fasting C-peptide (FCP) and C-peptide after 2h 75-g glucose load (PCP) were determined every 6 months. The levels of PCP and delta CP were higher in RSG group compared with those in SUs group after the 18th month. The PCP level (after the 12th month) and delta CP level (after the 18th month) in INS+/-RSG group were higher than those in INS group. Rosiglitazone combined with insulin wherever or not preserved beta-cell function in LADA patients after 3 years.