Nitric oxide (NO) free radicals appear to contribute to the pathogenesis of a number of disorders including diabetes mellitus. The aim of this study was to determine the effects of streptozotocin (STZ)-induced diabetes on nitric oxide (NO) metabolites in plasma and cerebellar nitric oxide synthase (NOS) activity. Further, it was of interest to determine whether an antioxidant, vitamin E, could reverse the STZ-induced effects. STZ significantly decreased cerebellar NOS but increased the level of plasma total nitrite + nitrate and the level of plasma nitrate. Supplementation with vitamin E effectively reduced the STZ-induced effects. Data demonstrate that vitamin E may serve as a protective antioxidant in STZ-induced diabetes.