Heat shock protein Hsp27 occurs in a complex pattern in human myocardial tissue. Normal and failing explanted human heart from patients with dilated cardiomyopathy (DCM) or ischemic heart failure (IHF), respectively, were analyzed by high resolution two-dimensional electrophoresis (23x30 cm) and Hsp27 immunostaining. Twelve Hsp27 spots in DCM samples were significantly altered in intensity and ten of these were significantly changed in IHF. Four spots (h1, h2, h4, h5) in DCM samples and three spots (h2, h4, h5) in IHF at a molecular mass of 28 kDa were decreased in intensity. In this study, investigating left ventricles of human myocardium, spot h4 was only detected in normal heart samples. On the other hand, spots with a lower molecular mass of 27 kDa (h14, h15, h17, h20, h21) and 22-23 kDa (46, h47, h50) increased in intensity in failing hearts, suggesting that some form of Hsp27 degradation occurs during heart failure.