/ T cells might play an important role in autoimmune conditions like inflammatory bowel disease (IBD). In the present study, we characterized the T cell receptor (TCR)- repertoire by complementarity determining region 3 (CDR3) spectratyping in the inflamed and noninflamed mucosa and in the peripheral blood of subjects with Crohn's disease and ulcerative colitis. In contrast to previously published data about / T cells, we rarely found oligoclonal expansions of / T cells specific only for the inflamed mucosa. The same dominant / T cell expansions were also present in the noninflamed colon. Furthermore, the peripheral / TCR repertoire was oligoclonal but clearly distinct from that in the inflamed intestine. Thus our results do not support a role for antigen-specific / T cells in IBD, and dominant / T cells of the peripheral blood are not likely to be derived from the inflamed gut. However, in several patients, the TCR--repertoire was highly diversified, whereas in others we observed a loss of dominant / T cell clones when inflamed and noninflamed mucosa were compared. In conclusion, those changes indicate that / T cells might play an important role in a subset of patients with IBD.