Type I diabetes mellitus is a metabolic disease caused by chronic immune attack against the insulin-producing cells of the pancreas. It has recently been shown that the clinical course of this disease can be interrupted by immune ablation and PBSCT. In this report, we describe our experience with this treatment modality in a series of eight cases. Patients with newly diagnosed type I diabetes were received treatment consisting of two to three plasmaphereses, hematopoietic stem cell mobilization with CY and G-CSF, collection of at least 3 × 10(6) per kg of CD34+ cells, and conditioning with CY and anti-thymocyte globulin followed by stem cell infusion. All patients became independent of exogenous insulin after the transplantation. One patient resumed low-dose insulin 7 months after transplantation. Six out of eight patients were given acarbose for better glycemic control after transplantation. All patients exhibited good glycemic control: the average HbA1c concentrations were 12.3% at diagnosis, and 5.6 and 6.2% at 3 and 6 months after transplantation, respectively. We conclude that at least temporary independence of exogenous insulin can be achieved in type I diabetes patients following immunoablation and reconstitution of the immune system with autologous PBSCs.