The authors have analysed gliadin specific, CD4+ T cells isolated from small intestinal biopsies of 23 adult coeliac disease patients (20 on a gluten-free diet and three untreated) and nine control patients. The biopsies were stimulated ex vivo with a peptic/tryptic digest of gliadin for 24 h, and activated T cells were positively selected with paramagnetic beads coated with an antibody against the interleukin-2 receptor. The T cells were expanded and tested for gliadin reactivity and HLA restriction. Gliadin specific, polyclonal T cell lines were recovered from biopsies of all 23 patients. Inhibition studies of T cell lines from 21 patients with anti-HLA monoclonal antibodies indicated predominant presentation of the gliadin antigen by HLA-DQ2 in T cell lines from 11 patients (lines from seven patients with complete MoAb inhibition, the remaining with incomplete inhibition) and incomplete inhibition by HLA-DR3 in lines from three patients. Nine gliadin specific T cell clones from six patients were established; all of these were HLA-DQ2 restricted. Gliadin specific T cells were not found in biopsies from the non-coeliac controls. Our findings demonstrate that gliadin reactive T cells are commonly found in the intestinal mucosa of CD patients and they support the notion that the majority of T cell recognize gliadin peptide(s) when presented by the disease associated DQ2 molecules.