Interleukin-10 (IL-10) is a pleiotropic cytokine and its main function is to limit and terminate inflammatory responses. Lung transplantation is a relatively young clinical field compared to the transplantation of other solid organs and long-term survival is still limited. Complications after lung transplantation include ischemia-reperfusion injury immediately after transplantation, acute rejection and infection within the first year after transplantation and chronic allograft dysfunction in form of bronchiolitis obliterans thereafter. In the setting of lung transplantation two key functions of IL-10 might be of interest: (1) the inhibition of inflammatory immune responses; and (2) the inhibition of T-cell mediated immune responses. In animal models, it has been shown that exogenous IL-10 is able to prevent posttransplant ischemia-reperfusion injury as well as to decrease acute rejection. It was also effective in preventing airway obliteration in an animal model of posttransplant bronchiolitis obliterans. Beneficial effects of IL-10 may be found early and late after lung transplantation. Location of IL-10 expression as well as the timing of administration seems to be important for the desired effects.