OBJECTIVE—To investigate whether long-term optimal glycemic control can be achieved without medication by transient continuous subcutaneous insulin infusion (CSII) and the possible mechanisms responsible for this remission. RESEARCH DESIGN AND METHODS—Newly diagnosed type 2 diabetic patients (n=138, fasting glucose＞11.1mmol/l) were hospitalized and treated with CSII for 2 weeks. Intravenous glucose tolerance tests (IVGTTs) were performed, and blood glucose, HbA1c, lipid profiles, proinsulin, insulin, and C-peptide were measured before and after CSII. Patients were followed longitudinally on diet alone after withdrawal of insulin. RESULTS-Optimal glycemic control was achieved within 6.3±3.9 days by CSII in 126 patients. The remission rates (percentages maintaining near euglycemia) at the third, sixth, twelfth, and twenty-fourth month were 72.6, 67.0, 47.1, and 42.3%, respectively. Patients who maintained glycemic control 12 months (remission group) had greater recovery of β-cell function than those who did not (nonremission group) when assessed immediately after CSII. Homeostasis model assessment of β-cell function (HOMA-B) and the area under the curve (AUC) of insulin during IVGTT were higher in the remission group (145.4±89.6 vs. 78.5±68.5, P=0.002, and 1,423.4±523.2 vs. 1,159.5±476.8 pmol-l•min-1, P=0.044). Change in acute insulin response was also greater in the remission group than that in the nonremission group (621.8±430.4 vs. 387.3±428.8pmol-l•min-1, P=0.033). CONCLUSIONS—Short-term intensive insulin therapy can induce long-term glycemic control in newly diagnosed type 2 diabetic patients with severe hyperglycemia. The improvement of β-cell function, especially the restoration of first-phase insulin secretion, could be responsible for the remission.