A broad-based, dynamic model of intrinsic coagulation is described. Non-anticoagulated whole blood was perfused through polyethylene tubing under standard conditions, and coagulation (cessation of flow) was monitored by pressure changes. The dynamic coagulation test (DCT) is a sequel to the shear-induced haemostasis, a platelet function test routinely performed prior to coagulation. DCT has two important advantages over stagnant overall clotting tests: i./DCT reflects platelet coagulant activities; selective activation by adenosine diphosphate or shear-stress or inhibition of platelets by prostacyclin greatly enhanced or prolonged dynamic coagulation, respectively. Furthermore, activation of platelets by plasminogen activators (streptokinase, t-PA) was manifested in a significantly shortened coagulation. ii./ DCT allows the rapid assessment of fibrin crosslinking, the mechanical stability of the clot formed. Antibody against factor XIIIa greatly prolonged the time until completion of clotting. In patients taking oral anticoagulant (n = 54), strong correlations were observed between DCT, the prothrombin time (INR) and the thrombelastograph measurements. It is concluded that this simple assay could be useful in the overall screening for coagulation abnormalities.