We evaluated cardiac troponin T (S-troponin T) versus CK MB in serum (S-CK MB) sampled 4, 10, 16, and 22 h after onset of acute symptoms in 207 consecutive cases admitted to our coronary care unit in Helsingborg, Sweden, May-October 1992. These were primarily classified into 106 acute myocardial infarctions (AMI) and 101 NOT-AMI cases by conventional cardiological criteria plus S-CK MB (mass). Time curves of S-troponin T and S-CK MB data were plotted for each individual case. Twelve of the 101 cases in the NOT-AMI group showed increased S-troponin T indicating ischemic myocardial injuries. The same cases also showed changes of S-CK MB (mass), though below its discriminator. Seven of these cases were reclassified as minor myocardial damage, constituting 25% of our 28 cases of unstable angina. The remaining five cases showed a combination of constantly increased S-troponin T and decreasing or low S-CK MB mass values as seen after a recent infarction. Consequently, the patient material was reclassified into 118 cases of ischemic myocardial injury (106 conventional AMI + 7 minor myocardial damage + 5 postinfarctions) and 89 cases of NOT-ischemic myocardial injury. The frequency distributions of the maximal S-troponin T and S-CK MB (mass) values of each case were plotted in double test evaluation histograms. For troponin T, discriminator 0.20 micrograms/L, clinical sensitivity for ischemic myocardial injury was 97% and specificity 99%. With a lower discriminator of 0.10 micrograms/L, sensitivity increased to 99% and specificity decreased to 89%. For S-CK MB (mass), discriminator 10 micrograms/L, sensitivity was 91%, specificity 98%. With a lower discriminator of 5 micrograms/L sensitivity increased to 96% and specificity decreased to 78%. We conclude that as a single routine test, S-troponin T is the marker of choice for early diagnosis of ischemic myocardial damage. The combination S-troponin T and S-CK MB (mass) provides additional, detailed information in reinfarction and postinfarction unstable angina pectoris.