Background: The cutaneous T cell attracting chemokine(CTACK/CCL27) is a pivotal chemokine in mediating lymphocytemigration into the skin, through the binding to the chemokinereceptor CCR10. The infiltration of skin by T cell appears to becrucial for the initiation and maintenance of inflammatory andautoimmune skin diseases, such as psoriasis.Objective: The aim of this study was to investigate the role ofCTACK in T cell homing in psoriasis. Which is a T cell mediateddisease.Patients and methods: This study included 30 patients withchronic plaque psoriasis and 30 healthy controls, in which wemeasured CTACK in the serum before and after therapy, [15patients received PUVA therapy and 15 received methotrexate].Results: CTACK level was significantly higher in patients thancontrols pretreatment [P value=0.001] such level decreasedsignificantly after treatment in both groups [ P value<0.05].Although both serum CTACK and PASI score decreased posttreatment , we could not detect a significant correlation, this wasalso true for pretreatment assessment, [P value> 0.05].Conclusion: CTACK might be significantly involved in thepathogenesis of psoriasis via mediating the migration oflymphocytes into the skin.