The main purpose of the present study was to determine whether any abnormalities in the response of fibrinolytic activity to venous occlusion could be observed in patients undergoing chronic hemodialysis (HD patients). A 10-min venous occlusion test was performed in 13 HD patients and in 9 healthy subjects. The arm opposite to the arteriovenous fistula was occluded in HD patients. The following factors were measured: tissue plasminogen activator (t-PA), plasminogen activator inhibitor 1 (PAI-1), plasmin-alpha2-plasmin inhibitor complex (PIC), stabilized fibrin degradation product (D-dimer), and von Willebrand factor antigen determined by enzyme immunoassay, and endothelin 1 by radioimmunoassay with two antibodies. Preocclusion levels of PIC, D-dimer, von Willebrand factor, and endothelin 1 were significantly higher and those of t-PA significantly lower in HD patients than in controls. During the occlusion, there was a positive correlation between the percent changes in t-PA and von Willebrand factor and between those in von Willebrand factor and PIC. There was no correlation between percent and absolute changes during the occlusion in endothelin 1 and those in t-PA, PAI-1, PIC, D-dimer, or von Willebrand factor. There was no significant difference between HD patients and controls as to the percent changes in hematocrit, t-PA, PIC, D-dimer and von Willebrand factor. HD patients demonstrated a significantly greater percent change in PAI-1 than controls. The mechanism by which endothelin 1 is released in response to the occlusion appears to differ from that for t-PA, PAI-1, and von Willebrand factor. PAI-1 may be readily released in response to stimuli to blood vessels in HD patients.