Repeated low doses of streptozotocin (STZ, 40 mg/kg body wt) gradually induce hyperglycemia in mice after a latent period of 5-7 days. The ability of STZ to induce hyperglycemia varies in different mouse strains. Repeated low doses of STZ fail to induce diabetes in T-cell-deficient mice, suggesting a crucial role of T-cells in the induction of diabetes by this procedure. Transfer of spleen cells from mice rendered diabetic by repeated low doses of STZ failed to induce hyperglycemia in the recipients. However, pretreating the recipients with a single low dose of STZ permitted efficient transfer of the diabetic state, suggesting that the immunologic reaction resulting in diabetes was actually specific for an STZ-modified beta cell.