Thrombolytic therapy in patients with acute myocardial infarction (AMI) changes the time-concentration curve of serum creatine kinase isoenzyme MB (CK-MB) and serum myoglobin. In this study, 60 AMI patients received thrombolytic therapy and acute coronary arteriography, or conservative treatment. Group one (n = 32) demonstrated a patent infarct-related artery after intravenous thrombolytic therapy; group two (n = 17) had an initially occluded coronary artery which became patent during catheterisation; group three (n = 11) did not receive thrombolytic therapy. Frequent serum CK-MB and myoglobin measurements showed that patients with acute coronary reperfusion had a rapid increase, an earlier peak value and less total release of both CK-MB and myoglobin to blood compared to AMI patients treated conservatively. The changes in serum myoglobin compared to CK-MB demonstrated an even more rapid, more uniform, and relatively greater increase. Measurements of serum myoglobin may be a useful non-invasive method for evaluation of thrombolytic therapy in AMI patients.