Coagulation and fibrinolytic abnormalities are common in patients with acute myeloblastic leukaemia (AML) like other forms of leukaemias. In this study, we investigated if total plasminogen activator inhibitor (PAI) activity, which is believed to increase in initial diagnosis and relapse in AML patients could be accepted as a relapse criterion or not. Total of 34 AML patients and 18 healthy volunteers were included in this study. The patients' diagnosis were based on clinical criteria as well as morphological, cytochemical, immunuphenotypic examinations of peripheral blood and bone marrow specimens. Total PAI activity was measured with Dade Behring Bericrom PAI reagent in BCS system. Total PAI activity was higher than 3.5 U/ml in 11 AML patients while it was normal (0.3-3.5 U/ml) in control group (P < 0.01). There was no significant difference in total PAI activity between AML subgroups (P > 0.05). We found significant difference in total PAI activity between patients who have active disease and remission. In conclusion, the total PAI activity could be accepted as a relapse and an initial diagnosis criterion of AML patients during follow up.