Different combinations of serum enzymes activity determinations are used in the diagnostics of myocardial infarction. The goal of the present paper was: 1) to assess the frequency of determinations of asparagine aminotransferase (AspAT) and to compare it with the frequency of determinations of creatinine phosphokinase (CPK) in patients hospitalized due to ischaemic heart disease in district hospitals, and 2) to assess to what extent the parallel determination of both enzymes effected to diagnostic classification of events according to The WHO MONICA Project. The analysis was done in 7406 hospitalized events registered with the clinical diagnosis of ischaemic heart disease (1810 myocardial infarctions, 402 acute coronary heart disease and 5194 other forms of ischaemic heart disease), registered in POL-MONICA Kraków Project in 1988-1993. Serum activity of AspAT was determined in over 90% events with either myocardial infarction or acute coronary heart disease. Number of determinations of CPK increased since 1990 and then, fluctuated from 15% to 36%. In 718 hospitalized events with clinical diagnosis of ischaemic heart disease, for whom both CPK and AspAT were determined, there was 96% observed agreement between diagnostic classification of events based on complains, ecg and alternatively: 1) both AspAT and CPK and 2) CPK only. Potential agreement beyond chance-kappa was 0.94 (almost perfect agreement). The parameters of the agreement were worse when AspAT only was used in the second option. The results indicate that efforts to increase the number of determinations of CPK in myocardial infarction diagnostics should be undertaken. At least for a part of events with myocardial infarction diagnosis confirmed by ecg and CPK tests, determination of AspAT is not necessary.