Monitoring coagulation parameters during thrombolytic therapy could be useful for prediction and treatment of haemorrhagic episodes. Technology based on dry reagent chemistry has been developed that allows rapid (< 10 min) assays on small samples of whole blood. The assay principle is based on the restriction of motion of paramagnetic particles during fibrin polymerization, and subsequent liberation of particle motion during fibrinolysis. This technology was used to monitor prothrombin time (PT), activated partial thromboplastin time (aPTT), fibrinogen levels and fibrinolysis profiles during thrombolytic therapy with tissue plasminogen activator for acute myocardial infarction. The PT and aPTT obtained with the COAG-1(tm) correlated well with conventional assays (r = 0.93 and 0.92 for PT and aPTT, respectively;/) = 0.0001). Fibrinogen estimates, obtained by COAG-2(tm) also correlated well with modified Clauss assays (r = 0.86, P= 0.0001). The rapid determination of the aPTTmay improve management of adjunctive anticoagulant therapy following thrombolysis. The fibrinolysis profile may be useful during thrombolytic therapy to verify that a lytic state has been achieved, to monitor the lytic state throughout therapy, and to verify that the lytic state normalizes once therapy has been completed.