T helper type 9 (T_H9) cells can mediate tumor immunity and participate in autoimmune and allergic inflammation in mice, but little is known about the T_H9 cells that develop in vivo in humans. We isolated T cells from human blood and tissues and found that most memory T_H9 cells were skin-tropic or skin-resident. Human T_H9 cells coexpressed tumor necrosis factor–α and granzyme B and lacked coproduction of T_H1/T_H2/T_H17 cytokines, and many were specific for Candida albicans. Interleukin-9 (IL-9) production was transient and preceded the up-regulation of other inflammatory cytokines. Blocking studies demonstrated that IL-9 was required for maximal production of interferon-γ, IL-9, IL-13, and IL-17 by skin-tropic T cells. IL-9–producing T cells were increased in the skin lesions of psoriasis, suggesting that these cells may contribute to human inflammatory skin disease. Our results indicate that human T_H9 cells are a discrete T cell subset, many are tropic for the skin, and although they may function normally to protect against extracellular pathogens, aberrant activation of these cells may contribute to inflammatory diseases of the skin.