In psoriasis, T-cell infiltration and epidermal hyperproliferation are key phenomena which are closely related. Our aim was to investigate the dynamics among T-cell subsets in relation to epidermal proliferation and clinical severity in psoriasis during treatment with an ultra-potent corticosteroid. Seven psoriasis patients were treated twice daily for 14 days with clobetasol-17 propionate ointment. Punch biopsies were taken at day 0, 3, 7 and 14. Epidermal proliferation marker Ki-67 and CD4+, CD8+, CD45RO+, CD2+ T cells were quantified by immunohistochemical techniques and image analysis. The clinical score declined significantly (60%; p<0.01) and a 47% reduction of Ki-67+ nuclei was observed after only 3 days (p<0.01). In the epidermis all investigated T-cell subsets were significantly reduced at day 14 (p<0.05). In the dermis, treatment resulted in a significant decrease of CD4+, CD45RO+ and CD2+ T cells, but dermal CD8+ T cells persisted. In psoriasis, reduction of clinical severity and epidermal proliferation during the early phase of topical corticosteroid therapy cannot primarily be the result of decreased T-cell subsets. Furthermore, selective persistence of dermal CD8+ T cells was observed, which might be associated with disease relapse.