The activity of the inhibitor of activated Stuart factor (anti-Xa) was evaluated together with the activity of the antiactivator of plasminogen (antiplasminogen) and the amount and nature of the fibrinogen/fibrin degradation products (FDP), as indicators of the existence of the risk for hypercoagulability in patients with acute and recent myocardial infarction (AMI and RMI, respectively). The activity of anti-Xa was diminished in the AMI group with a p < 0.001. The antiplasminogen activity was increased in both groups with a p < 0.001; on the other hand, the amount of FDP was increased in the AMI patients and they were of the ‘early’ type, while in the RMI group the increase was not as marked, but the FDP were of the ‘late’ type. In both groups the euglobulin lysis time was very prolonged, while the plasminogen did not vary significantly. The tests described appear to be valuable tools for studying the status of the cardiovascular system during cardiac rehabil