When multiple low doses (30 mg/kg body wt) of streptozocin were given to CD-1 mice, diabetes associated with L3T4 T-lymphocyte- and B-lymphocyte-predominant insulitis occurred. Thus, a model of type I (insulin-dependent) diabetes was obtained. To treat these diabetic mice, we administered lobenzarit (CCA), a newly synthesized immunomodulator. CCA (2 or 10 mg/kg body wt) significantly inhibited the progression of diabetes by suppressing the severity and incidence of insulitis. Insulin contents of the pancreas were preserved. The possibility that autoimmune-related diabetes can be treated with CCA warrants further attention.