The relation between myocardial functional changes and the apoptosis-related proteins in patients with dilated cardiomyopathy (DCM) has not yet been reported. The purpose of this study was to assess this issue through the use of dobutamine stress echocardiography. A total of 81 segments of left ventricles (from 6 patients with DCM) were collected in this study. Segments from another 5 patients who had died of noncardiac causes were used as the control. Apoptosis-related proteins (bax, bcl-2, and p53) and apoptosis were evaluated in these segments by immunocytochemical stain and terminal deoxynucleotidyl transferase-mediated DNA nick end-labeling assay. There were 26 segments with dobutamine-induced contractile reserve. There were significant differences in numbers of segments with overexpression of bcl-2 and bax in the study and control groups. However, p53 was not found in either group. The total terminal deoxynucleotidyl transferase-mediated DNA nick end-labeling-positive nuclei in explanted hearts of DCM was 0.73%. The myocardial contractile reserve was inversely associated with an overexpression of bcl-2 (P <.01) rather than bax. In conclusion, the expression of bax and bcl-2 proteins in patients with DCM is enhanced and independent of p53. Loss of contractile reserve is associated with overexpression of bcl-2 protein in failing myocardium.