Type 1 diabetes results from the loss of insulin-producing pancreatic beta cells. T cell-mediated autoimmunity has been suggested to play a crucial role in the destruction of beta cells. Recently local balance between cytokines in the insulitis lesions has been implicated as an important immunologic factor in determining whether diabetes will delvelop or not. In the present study, effects of Complete Freund´s adjuvant treatment, which has been known to prevent diabetes in NOD mice, on the expression of cytokine and iNOS gene in the pancreata of NOD female mice were investigated. Histologic examination of pancreatic islets showed that CFA treatment could suppress insulitis. Interestingly CFA treatment was found to stimulate expression of multiple cytokines in the pancreata of NOD mice. Expressions of IL-l0, IFN-g, and iNOS were significantly enhanced, whereas expressions of IL-2, IL-4, and TNF-a were less affected. No changes in IL-12 or TGF-b expression was observed. These results suggest that alterations in cytokine balance, especially an increased expression of IL-10, in the pancreas by CFA treatment may play a role in the prevention of beta-cell destruction.