To observe the effects of interleukin (IL)-1 beta and IL-6 on nitric oxide (NO) production, islet cell DNA and insulin content, and MTT assay of rat pancreatic islets of Langerhans.Isolated pancreatic islet cells from SD rats were cultured in monolayer in vitro. Nitrite production, islet cell DNA and insulin content, and MTT assay in rat pancreatic islet cells incubated with IL-1 beta and IL-6, singly or in combination, were measured. The levels of these parameters of the cytokines in the absence and presence of N(G)-monomethyl-L-arginine (L-NMMA), an inhibitor of nitric oxide synthetase, were compared.IL-1 beta induced a significant increase in nitrite production, a decrease of islet cell DNA and insulin content and reduction of cell activity (MTT, P < 0.001); these changes were blocked by L-NMMA (P < 0.001). IL-6 produced no significant change in those parameters (P > 0.05). The combination of IL-1 beta and IL-6 increased NO production, decreased islet cell DNA and insulin content and reduced cell activity (P < 0.001); the changes were similar to those with IL-1 beta alone (P > 0.05).The cytotoxic effects of IL-1 beta on pancreatic islets might be mediated by NO. IL-6 may not be directly cytotoxic to pancreatic islets. It may be related with the fact that IL-6 does not induce NO production.