Abstract: Objective To investigate the clinical implications of cardiac troponin I (cTnI), myoglobin (Mb), creatine kinase (CK) and creatine kinase isoenzyme (CK-MB) in patients with acute myocardial infarction (AMI).Methods The serum concentrations of cTnI and Mb were determined in 50 patients with AMI 2 to 4 h after chest pain onset and compared with those measured in 50 age-matched healthy subjects.Results The serum levels of cTnI, CK-MB and CK in patients with AMI were significantly higher than those in the control group. Mb levels in AMI group were above the normal range. Mb, CK-MB, CK and cTnI reached the peak levels at 8±2.2, 18.1±3.2, 19.4±4.1 and 18.6±2.9 h after the onset, respectively, and their levels increased with the aggravation of AMI and were reduced to the normal levels with the amelioration of the disease. All the 4 indices were normal in the control group.Conclusion cTnI and Mb are reliable biochemical markers for early diagnosis of AMI and the changes in their serum levels have clinical significance in diagnoses and prognostic judgment of AMI.