Cyclosporin A and methotrexate are highly effective drugs in the treatment of psoriasis. It was hypothesized that these therapies might modulate T helper cell cytokine secretion patterns or T cell migration patterns. Flow cytometric determination of interferon-gamma (IFNgamma) and interleukin 4 (IL4) producing T helper cell frequencies, as well as of cutaneous lymphocyte associated antigen (CLA) expressing T cell frequencies was performed in patients suffering from severe psoriasis, before, during, and after a scheduled immunosuppressive regimen with either cyclosporin A or methotrexate. Both cyclosporin A and methotrexate treatment reduced the psoriasis area severity index score after 12 weeks of treatment. Cyclosporin A treatment reduced the frequencies of IL4-producing CD4(pos) T cells, without significantly affecting the T helper 1 to T helper 2 (Th1/Th2) balance but in conjunction with the decreasing number of peripheral blood eosinophil counts. In methotrexate-treated patients, the Th1/Th2 balance was unaffected. Cessation of both therapies resulted in increased numbers of IFNgamma- as well as IL4-producing CD4(pos) T cells as compared to before initiation of oral therapy. Methotrexate, but not cyclosporin A, treatment reduced the frequencies of circulating skin-homing CLA(pos) T cells. This effect was reversed by 4 weeks after withdrawal of methotrexate therapy. We conclude that (1) neither cyclosporin A nor methotrexate affects the balance between Th1 and Th2 cells; (2) exaggerated cytokine production by T helper cells after cessation of oral cyclosporin A or methotrexate drug treatment may contribute to the reappearance of psoriatic skin lesions; and (3) decrease of circulating skin-homing T cells may be responsible for part of the therapeutic effect of methotrexate in severe psoriasis.