Psoriasis is a T lymphocyte–driven systemic inflammatory disease. Regulatory T cells (Tregs) are essential for establishing and maintaining immune tolerance. In this study, we found that patients with psoriasis and healthy controls had comparable percentages of circulating CD4+CD25+FOXP3+ Tregs, but psoriatic Tregs had reduced suppressive function. Thereafter, mRNA arrays were performed to study the gene expression profile of psoriatic Tregs. Psoriatic Tregs expressed high levels of a T helper type 1–like transcription factor and cytokines such as T-bet and IFN-γ.