In summary, we established that a significant production of the monokines interleukin-6, tumor necrosis factor apha, and interleukin-1 occurred during orthotopic liver transplantation whereas the lymphokines interferon gamma and interleukin-2 were not detected. Levels of interleukin-6 reached their maximum values before and especially at the end of the anhepatic phase. They remained high after the anhepatic phase, i. e. after reperfusion of the new livers. Tumor necrosis factor alpha and interleukin-1 reached their maximum values after the anhepatic phase. Not only were interleukin-6, tumor necrosis factor alpha, and interleukin-1 present in the serum but they could also be detected in the bile produced by these new livers. Mechanisms of monokine production during orthotopic liver transplantation is multifactorial in origin and further studies will have to evaluate the relative contribution of the various factors involved. The possibility of an association between peroperative monokines and transplant outcome and their potential clinical implication will have to be elucidated.