Plasma fibrinopeptide B beta 15-42 was significantly high in undialyzed and hemodialyzed chronic renal failure (CRF) patients, indicating that the fibrinolytic system as well as the coagulation system is stimulated. There are two kinds of plasminogen activators (PA) for the fibrinolytic system: urokinase (UK) and tissue-type PA (t-PA). PA activity of peripheral leukocytes from healthy volunteers, continuous ambulatory peritoneal dialysis (CAPD) patients and hemodialysis (HD) patients was measured and compared. Peripheral leukocyte PA in the euglobulin fraction was purified using zinc-chelate-Sepharose 6B column and Concanavalin A-Sepharose column chromatography. The different PA activity was quantitatively identified by electrophoretic enzymography and was confirmed using antibody against UK and t-PA. PA activity of peripheral leukocytes was significantly higher in HD patients on the cupro-ammonium processing membrane dialyzer than in CAPD patients and healthy volunteers. All PA activity in the three groups was UK, and t-PA was not detected. This suggested that the inflammatory response was continuously induced in HD patients, resulting in the induction of PA activity of the leukocytes and plasma, and that different mechanisms were involved for the synthesis or secretion of UK and t-PA.