We analyzed the time course of serum creatine kinase (CK), the CK MB isozyme, lactate dehydrogenase (LDH), and serum glutamic-oxaloacetic transaminase (SGOT) activity and calculated rates of increase and decline for CK in 24 consecutive patients with acute myocardial infarction (AMI) who received intracoronary thrombolytic therapy. In 19 patients with successfully reperfused infarcts, peak CK activity occurred at 14.1 +/- 1.1 hours after onset of symptoms, the maximal rate of CK rise was 595 +/- 102 IU/L/hr, and the fractional disappearance rate (Kd) was (86 +/- 6) X 10(-5)/min. The peak CK MB activity occurred at 12.9 +/- 0.8 hours and the MB Kd was (223 +/- 39) X 10(-5)/min. In five patients in the nonreperfused group the peak CK (24.9 +/- 4.5 hours) and CK MB (22.7 +/- 3.3 hours) activity occurred later, the maximal rate of CK rise (281 +/- 37 IU/L/hr) was less, and the CK Kd [(68 +/- 5) X 10(-5)/min] and MB Kd [(116 +/- 28) X 10(-5)/min] were lower. The peak CK, CK MB, cumulative CK release, and area under the curve were not different. Except for a shortened time to peak SGOT in the reperfused (17.1 +/- 1.3 hours) compared with the nonreperfused (29.1 +/- 5.6 hours) groups, the time course of LDH and SGOT were not different. Thus, the initial serum CK kinetics and time to peak SGOT may be useful in assessing the reperfusion status in patients with AMI receiving thrombolytic therapy without coronary angiography or in those who may have spontaneous recanalization.