AbstractDifferent parameters of fibrinolytic systems like t‐PA, PAI, D‐dimer, and inhibitors of blood coagulation, i.e., protein C (PC), protein S(PS), and antithrombin III (AT‐III), have been studied in cases of acute malaria due toPlasmodium falciparumandplasmodium vivaxinfection, and these patients were followed up. It was observed that the plasma PAI‐1 was very high in cases ofP. falciparummalaria infection as compared to normal controls andP. vivaxinfection. The changes in complicated cases ofP. falciparumwere remarkable as compared to uncomplicated ones. The PC, PS, and AT‐III levels were also low inP. falciparum, particularly so in complicated cases, and were normal inP. vivaxinfection. The factor VIII R:Ag levels were invariably high in acute malaria. On follow‐up of some of these cases the values came back to normal after the antiparasite treatment. The monocyte procoagulant activity was found to be significantly higher inP. falciparuminfection as compared to that ofP. vivaxinfection. All these findings therefore contribute towards the production of a hypercoagulable state inP. falciparuminfection and partly explain the complications ofP. falciparuminfection like cerebral malaria. Am. J. Hematol. 54:23–29, 1997 © 1997 W