With its antiinflammatory and immunosuppressive properties interleukin-10 (IL-10) plays a dominant role in several immune reactions including regulatory mechanisms in the skin. The overexpression of this mediator has been reported in some inflammatory dermatoses as well as in various skin tumors. These observations are of importance since they may explain the limitation of hyperinflammatory conditions as in eczemas and erythemas on the one hand and the suppression of an adequate antitumor response and thereby the progression of malignant tumors on the other hand. Moreover, elevated IL-10 expression might contribute to an enhanced risk of development of microbacterial superinfections, a frequent finding in several dermatoses, and might also be involved in the pathogenesis of connective tissue diseases. In contrast, recent studies indicate a relative IL-10 deficiency in psoriasis. Early clinical data from psoriatic patients treated with recombinant human IL-10 suggest the therapeutic potential of this cytokine and underline its impact on the regulation of the skin immune system.