Regulatory T cells (Treg) are a specialized subpopulation of T cells that act to suppress inadequate immune response. Psoriasis is recognized as a T -cell driven immune-mediated systemic inflammatory disease with skin manifestation. Effective therapeutical approach to treat psoriasis is Goeckerman therapy (GT ). The aim of this study was to compare the number of Treg in the peripheral blood of 27 psoriatic patients and 19 controls and to evaluate the influence of GT on Treg population in peripheral blood of patients with psoriasis. There was no significant difference in the relative number of Treg cells in the peripheral blood of healthy blood donors and patients with psoriasis before initiation of GT (P = 0.2668). In contrary, the relative number of Treg cells in peripheral blood of patients with psoriasis after GT was significantly higher than those found in healthy blood donors (P = 0.0019). Moreover, the relative number of Treg is significantly increased in psoriatic patients after Goeckerman therapy compared to the pre-treatment level (P = 0.0042). In conclusion, this significant increase in Treg count after GT is probably associated with amelioration of inflammation by GT , as disease activity expressed as PASI decreased in our patients by GT (P = 0.0001)., Kateřina Kondělková, Doris Vokurková, Jan Krejsek, Lenka Borská, Zdeněk Fiala, Květa Hamáková, Ctirad Andrýs, and Literatura 39