Non-obese diabetic (NOD) mice spontaneously develop diabetes. Ourselves and others have previously shown that oral and nasal administration of insulin or glutamic acid decarboxylase (GAD) suppresses development of diabetes in the NOD mouse and that this suppression appears secondary to the generation of regulatory T cells that act by secreting anti-inflammatory cytokines such as IL-4 and TGF-β. In the present study, we analysed cytokine patterns associated with mucosal administration of insulin B-chain, B-chain peptide 10–24 and GAD peptide 524–543 and derived lines and clones from mucosally-treated animals. Mice were fed five times (400–600μg/feed) or nasally-treated three times (60μg/application), and 2 days after the last treatment were immunized in the footpad with the mucosally administered antigen in CFA. Primary immune responses in the popliteal lymph node were measured 10 days after immunization and lines and clones were then established from the primary cultures. There was significantly less IFN-γproduction in mucosally-treated mice associated with increased production of IL-10 and TGF-β. The nature of the antigen appeared to determine cytokine production as the B-chain given either orally or nasally primed for TGF-β responses, whereas mucosally administered B-chain peptide 10–24 primed for IL-10. T cell clones, established from draining lymph nodes of fed or nasally-treated animals, secreted IL-4, IL-10 and TGF-βwhereas those from non-fed mice secreted IL-2 and IFN-γ. Transfer of Th1 lines with splenocytes from diabetic NOD mice into NOD or NOD/SCID animals accelerated diabetes, whereas transfer of Th2 lines suppressed the development of diabetes. Our results further support a role for Th2-type cells in the regulation of diabetes in NOD mice.