Recent studies have suggested a close relationship between CD4⁺FOXP3⁺ regulatory T cells (Tregs) and proinflammatory IL-17-producing T helper cells (T_H17) expressing the lineage-specific transcription factor RORγt. We report here the unexpected finding that human memory Tregs secrete IL-17 ex vivo and constitutively express RORγt. IL-17-secreting Tregs share some phenotypic and functional features with conventional T_H17 cells, expressing high levels of CCR4 and CCR6 and low levels of CXCR3. However, unlike conventional T_H17 cells, they express low levels of CD161 and mostly fail to cosecrete IL-22 and TNF-α ex vivo. Ex vivo secretion of IL-17 and constitutive expression of RORγt by human memory Tregs suggest that, in addition to their well-known suppressive functions, these cells likely play additional, as yet undescribed, proinflammatory functions.