To clarify the relationship between the results of intracoronary thrombolytic therapy (ICT) and fibrino-coagulation in patients with acute myocardial infarction (AMI), the thrombin-antithrombin III complex (TAT) and fibrinopeptide A (FPA), as indices of accelerated coagulation, and the plasmin- alpha 2-plasmin inhibitor complex (PIC), as an index of accelerated fibrinolysis in peripheral blood, were measured just before and after heparin injection (5,000 U), and immediately after ICT. Twenty-four patients with AMI were divided into 2 groups according to the results of ICT; successful ICT (group S) and unsuccessful ICT (group F). As a control group (group C), 14 age-matched normal volunteers were also studied. The levels of TAT and FPA before ICT were significantly higher in groups S and F than in group C (p < 0.01). The TAT level before ICT in group F was higher than that in group S (p = 0.07), however, the TAT, FPA and PIC levels showed no significant differences between groups S and F at each sampling time. TAT/PIC before ICT was significantly higher in group F than in group S (F: 0.026 +/- 0.020 vs S: 0.008 +/- 0.004, p < 0.05), whereas there was no remarkable difference in FPA/PIC between groups S and F. These results indicate that hyper-coagulation had occurred in the AMI cases and that coagulation had been more accelerated in group F. TAT/PIC might be an index of the equilibrium of the fibrino-coagulating system. Therefore, TAT/PIC measurement before thrombolytic therapy may be more useful than TAT measurement alone for evaluating recanalization in ICT.