Interleukin-19 (IL-19) is a member of the IL-10 family of cytokines. The last ten years from the finding of IL-19, investigations underline the role of IL-19 in the immunological diseases. It is known that expression of IL-19 is increased in the epidermis of patients with psoriasis, which is a Th1 dominant disease. Increased concentration of IL-19 has also been found in the serum of patients with asthma, which is a Th2 dominant disease. There is an increasing body of data demonstrating that IL-19 is associated with the pathogenesis of both Th1 and Th2 dominant diseases. Regarding the role of IL-19 on the innate immunity and inflammation, interestingly, in vitro studies have shown that lipopolysaccharide can stimulate human monocytes and macrophages to upregulate the expression of IL-19. IL- 19 is upregulated in macrophages after infection and lessens inflammation by suppressing the production of tumor necrosis factor-α, IL-6 and IL-12, but not by inducing IL-10. In addition, IL-19-deficient mice are susceptible to experimental colitis induced by dextran sodium sulfate, a disease which is characterized by excessive inflammatory responses of local macrophages and epithelial cells to intestinal microflora. In this review, we discuss our current understanding of the role of IL-19 in autoimmune and inflammatory diseases.