The relationship between lytic state variables and ex vivo clot lysability was investigated in blood drawn from patients during streptokinase administration for acute myocardial infarction. A lytic state was already evident after 5 min of treatment and after 20 min the plasminogen concentration had decreased to 24%, antiplasmin to 7% and fibrinogen 0.2 g/l. Lysis of radiolabeled retracted clots in the patient plasmas decreased from 37 +/- 8% after 5 min to 21 +/- 8% at 10 min and was significantly lower (8 +/- 9%, p