Psoriasis is a common inflammatory skin disease that is thought to be mediated by activated T cells. In this study, the complementarity-determining region 3 (CDR3) in T cell receptors was examined for a common sequence motif among the T cells infiltrated in psoriatic lesional skin. A common specific CDR3 motif (Vbeta13-DWTSGV-Jbeta2.7) in lesions from psoriasis patients was identified by polymerase-chain-reaction-based spectratyping analysis and DNA sequencing. In addition, VDJ rearrangement with highly homologous amino acid composition in the CDR3 was observed in Vbeta15 of T cell receptors in lesions derived from psoriatic patients. Remarkably, T cell receptors containing the Vbeta13-DWTSGV-Jbeta2.7 were also found in the clinically normal skin from the psoriasis patients, which might seem to be responsible for the artificial production of psoriatic lesions. The identified CDR3 motif was highly expressed in cutaneous lymphocyte antigen (CLA+) cells of peripheral blood mononuclear cells from psoriasis patients compared with the expression in healthy individuals. This result showed that the infiltrated CLA+ T cells with the Vbeta13-DWTSGV-Jbeta2.7 motif in peripheral blood mononuclear cells from psoriasis patients might be involved in the development of psoriatic lesions. In addition, the results in this study suggest that the infiltrated T cells with the Vbeta13-DWTSGV-Jbeta2.7 motif in psoriatic lesions may be involved in the pathogenesis of psoriasis.