Platelets play a central role in primary hemostasis. The role of the coagulation mechanism during early stages of hemostasis is less clear, although increasing evidence is emerging indicating the ultimate importance of the factor VII (FVII)-tissue factor-dependent coagulation system in providing the first thrombin molecules necessary for the platelet activation to occur. Supporting this, early fibrin formation has been reported to occur within the bleeding time wound and infusion of recombinant FVIIa (rFIIa) has been shown to shorten the bleeding time in rabbits. We have investigated whether infusion of rFVIIa would enhance fibrin formation in bleeding time wounds in patients with thrombocytopenia as reflected by a shortening of the bleeding time. A reduction of the bleeding time was found in 55/105 cases (52%). The decrease was significantly more pronounced when the platelet count exceeded 20 x 10(9)/l. With the exception of an anaphylactoid reaction in 1 patient, no major adverse reactions related to the study drug were observed. Nine infusions of rFVIIa were given to 8 thrombocytopenic patients with overt bleeding. One patient received two infusions. Bleeding decreased in all patients and stopped in 6 patients.