Myocyte necrosis has been considered to play a fundamental role in the pathophysiology of congestive heart failure (CHF), which has usually evolved as a consequence of depletion of compensatory mechanisms and contractile reserve of myocardium. Elevated levels of creatine kinase MB (CK-MB) and troponin I (Tn-I) have been regarded as biochemical markers of myocyte necrosis. This study was planned to investigate the specificity and sensitivity of Tn-I and CK-MB in CHF and to examine the correlation of these markers with disease severity. A total of 104 patients (38 female, 66 male; mean age, 66 y [range, 36-89]) with symptoms and signs of heart failure on admission and with a reduced left ventricular ejection fraction (EF; by transthoracic echocardiography) were labeled "the patient group," and 58 patients (40 female, 18 male; mean age, 61 y [range, 34-77]) with no signs or symptoms of CHF and with a normal EF detected by transthoracic echocardiography were included in the study as "the control group." Left ventricular EFs, end-diastolic diameters, and end-systolic diameters of patients in both groups were measured. Blood samples were drawn from all patients in both groups on admission, so that levels of CK-MB and Tn-I could be measured. All patients in both groups also underwent coronary angiography. Conditions leading to elevation of CK-MB or Tn-I were considered exclusion criteria. The 2 groups failed to show any significant differences in terms of mean age and the presence of coronary artery disease, hypertension, or diabetes mellitus (P >.05). Mean EF in the patient group was lower than that in the control group (P <.05). Mean CK-MB and Tn-I in the patient group were significantly higher than in the control group (P <.05). In the patient group, hypertensive patients were found to have significantly higher mean values of CK-MB than were seen in normotensive patients in the same group (P <.05). In the patient group, 52 cases were considered to be class I-II (New York Heart Association [NYHA]) (group 1), and 52 were considered to be class III-IV (group 2). Group 1, group 2, and the control group did not differ significantly from one another with regard to the presence of coronary artery disease, hypertension, and diabetes mellitus (P >.05). The mean EF in group 2 was significantly lower than that in group I and in the control group (P <.05); the mean EF in group I was significantly lower than that in the control group (P <.05). Group 1 values did not differ significantly from those of group 2 or the control group in terms of enzymatic markers (P >.05), but group 2 had significantly higher mean values of CK-MB and Tn-I than were noted in the control group (P <.05). The uphill course of CK-MB and Tn-I values from the control group to group 2 (NYHA class III-IV) was statistically significant (P <.05). Serum concentrations of CK-MB and Tn-I may become elevated in severely symptomatic patients with CHIF (particularly NYHA class III-IV), demonstrating a relationship between clinical severity of the disease and elevation of myocardial enzymes (CK-MB and Tn-I).