Nasal application of soluble Ags leads to Ag-specific suppression of systemic immune responses. This tolerance can be transferred to naive mice by CD4+ regulatory T cells (T R cells) from the spleen, but little is known about the induction of mucosal T R cells in vivo. To investigate the induction of T R cells in the nose-draining cervical lymph node (CLN), CD4+ T cells from DO11. 10 OVA TCR transgenic mice were transferred to BALB/c recipients. Within 48 h after nasal OVA application, CD4+ DO11. 10 T cells in CLN, but not in the peripheral lymph node, had divided. Similarly, nonmucosal (im) OVA application also induced CD4+ DO11. 10 T cells to proliferate in the draining inguinal lymph node (ILN), yet more vigorously and with different kinetics than the CD4+ DO11. 10 T cells in CLN. Functional analysis revealed that only proliferating CD4+ DO11. 10 T cells from CLN, and not ILN, could transfer tolerance to naive recipients. CD4+ DO11. 10 T cells from CLN were phenotypically similar to CD4+ DO11. 10 T cells from ILN, however, in CLN a higher percentage of CD25+ proliferating CD4+ DO11. 10 T cells were detected compared with ILN. CD25 is not a discriminative marker for mucosal T R cells because both CD25+ and CD25− CD4+ DO11. 10 T cells from the CLN could suppress delayed type hypersensitivity responses in adoptive transfer. These findings demonstrate that although striking similarities exist between the differentiation of T R and effector T cells, this does not include their function. We are the first to demonstrate that functional T R cells, which reside within both CD25+ and CD25− subsets, can be isolated from CLN as early as 3 days after nasal OVA application.