Cytokines are crucial inflammatory mediators involved in the development of immune response leading to allograft rejection. We investigated the cytokine patterns in patients sera from cases of acute rejection episodes (ARE), chronic rejection (CR), and long-term stable courses (STABLE). The project included 20 patients with ARE, 20 with CR, and 15 with at least a 5-year stable course. Serum samples collected at the time of rejection diagnosis were cytometrically tested for concentrations of interleukin (IL) 2, IL-4, IL-6, IL-10, interferon (IFN) gamma, and tumor necrosis factor alpha. No significant differences between investigated groups were observed before transplantation (P > .05). Significant differences were observed among the groups in serum levels of IFN-gamma, IL-4, IL-6, and IL-10. Our data suggested that distinct serum cytokine patterns were present among various states of kidney allograft function. ARE was characterized by a mixed cytokine pattern with elevated IL-10 and IFN-gamma compared with the STABLE patients. The cytokine pattern in CR patients, in turn, was characterized by elevated levels of IL-4, IL-6, and IL-10 and decreased levels of IFN- gamma compared with both STABLE and ARE subjects. Our results suggested that the T(H)2 response may contribute to the initiation and/or maintenance of CR, because IL-4, IL-6, and IL-10 serve as growth and differentiation factors for B cells to increase antibody production. We also observed up-regulated production of IFN-gamma and down-regulation of T(H)2 cytokines among patients with stable long- term graft function.