Summary Haemostatic parameters were studied in 28 adult patients (pts) treated for acute myeloid leukaemia (AML) using an intermediate dose of AraC (1000 mg/m 2 – 6 days) and mitoxantrone (6 mg/m 2 – 6 days) as the second regimen after the ‘3 and 7’ regimen (18 pts were in complete remission — CR and 10 had AML resistant to ‘3 and 7’). Increased levels of plasminogen activator inhibitor (PAI) activity (p<0.05) were observed during chemotherapy. In pts with resistant AML higher levels of fibrinopeptide A (FPA) were found (p<0.05) than in CR pts. During aplasia all pts suffered from infectious complications, 18 from sepsis and 10 from fever of undetermined origin. During the period of infection (with maximum on days 17 and 24) increased levels of PAI (p<0.05) and FPA (p<0.05) and decreased values of plasminogen, alpha 2 antiplasmin and antithrombin III activities were measured (all p<0.05). Tissue plasminogen activator, protein C and fibrin(ogen) degradation products were normal throughout the observation. Thrombotic complication (catheter-related subclavian vein thrombosis) occurred in only one patient on day 12 (all the parameters measured were within the norm that day). Haemostasis was compensated throughout observation and all changes found were clinically irrelevant. Authors suggest that chemotherapy application as well as periods of infectious complications should be marked in haemostatic studies and that these two pathophysiological mechanisms (together with remission status) should be taken into account before making conclusions.