The goal of this research was to assess the performance of serum creatine kinase (CK), creatine kinase MB (CKMB) [mass and activity], troponin I (TnI) and troponin T (TnT) in the diagnosis of acute myocardial infarction in patients admitted to the Coronary Care Unit at Queen Alia Heart Institute, Amman, Jordan, between March and July 2001. Blood samples collected for cardiac enzyme determination (CK, CKMB activity) were stored at -20°C for later determination of CKMB mass [Abbott Axsym, Ortho Clinical Diagnostics (OCD) ECi and Roche Elecsys], TnI (Abbott Axsym) and TnT (Roche Elecsys). The relative index (RI = CKMB mass/CK), for CKMB mass measurements, was calculated. Clinical notes and/or discharge diagnosis for each patient were reviewed to obtain the diagnosis of acute myocardial infarction. Fifty samples were from acute myocardial infarction (AMI) patients. Area under Receiver Operating Curve values were: CK 0.56, CKMB activity 0.72, percentage of CKMB activity 0.73, CKMB mass (Abbott) 0.76, CKMB mass (Roche) 0.77, CKMB mass (OCD) 0.78, RI (Roche) 0.83, RI (Abbott) 0.87, RI (OCD) 0.86, TnI 0.95, TnT 0.94. Sensitivity: TnI 88%, TnT 93%; specificity TnI 99%, TnT 99%. There was no significant difference in performance between TnI and TnT assays or between any of the CKMB mass measurements. Present results show that TnI and TnT are better cardiac markers than CK and CKMB, mass or activity.