The cytokine interleukin-19 (IL-19) is a member of the IL-10 family that includes IL-20, IL-22, IL-24, and IL-26. Previous studies indicated that IL-19 is produced by keratinocytes, epithelial cells, macrophages, and B-cells. Especially, the number of IL-4-producing T cells increased, whereas the number of IFN-γ-producing T cells decreased when naive T cells from healthy people were cultured in the presence of IL-19. There is an increasing body of data demonstrating that IL-19 is associated with the development of type 1 helper T cell-responses, although IL-19 was originally associated with the development of type 2 helper T cell-responses. In this review, we will attempt to discuss current knowledge about the role of IL-19 on several T cell response-mediated inflammatory diseases including inflammatory bowel disease and hypersensitivity.