Psoriasis vulgaris is a common HLA‐associated inflammatory skin disease. Although its etiology is still unknown, it is thought to involve T cell‐mediated inflammatory mechanisms. In examining the lesional psoriatic TCR β chain (TCRB) usage in a pair of identical twins concordant for psoriasis, we observed repetitive TCR VDJ rearrangements which indicated antigen‐specific oligoclonal T cell expansion. Several of these TCRB rearrangements were identical or highly homologous in the amino acid composition of the complementarity determining region 3 (CDR3), suggesting that T cells with these TCR might be important for disease manifestation. This conclusion was strengthened by TCR analysis of other psoriasis patients. Several repetitive lesional TCRB rearrangements were found that were similar to the conserved CDR3 seen in the twins. Since TCR antigen specificity is largely determined by the β chain CDR3, selection of T cells with conserved TCRB CDR3 motifs could indicate the presence of a common antigen as a major target of the lesional psoriatic immune response.