As our knowledge of the cytokine network in experimental transplant models grows, we need to understand how and to what extent cytokines mediate the various donor-directed immune events in clinical situations. This overview of clinical cytokine measurements shows that specific intragraft cytokine messenger RNA (mRNA) expression profiles can be associated with acute rejection, that they may reflect the efficacy of immunosuppression, and that they can identify patients at risk for the development of early chronic rejection. The literature also shows that acute rejection and immunological quiescence in humans are not restricted to the cytokine patterns defined in the type 1/type 2 paradigm. This apparent lack of association may be caused by the immunosuppression used in the clinic but may also be the result of the infinite diversity of donor and recipient factors, in which polymorphisms in cytokines and cytokine receptor genes may play a central role.