Objectives:The present study in vestigated the presence and significance of serum antibody against human myocardial mitochondria in patients with virus myocarditis (VMC) and dilated cardiomyopathy (DCM). 　　Methods:The human myocardial mitochondtia were used as antigen to detect serum autoantibody by immuno-dot blot in 29 VMC patients,24 DCM patients,33 patients with other cardiac (OCD) and 20 healthy blood donor (HBD).The antigen molecular weight was detected by Western blot. 　　Results:①Positive autoantibody against human myocardial mitochordria was found in 41.4% in VMC and 41.7% in DCM patients,which were much higher than 6.1% in OCD or 0% in HBD patients.②Cardiac troponin T was elevated in 43.8% of autoantibody-positive VMC and DCM patients,which was much higher than 12.0% in autoantibody-negative VMC and DCM patients (p＜0.05).③The antigen molecular weight of human myocardial mitochondria was 30KD. 　　Conclusions:①The presence of autoantibody against supports that concept that is responsible for the development of VMC and DCM.Autoantibody is one of the factors that give rise to cardiac injury.The antibody detection may serve as a diagnostic index for VMC and DCM.②The specific antigen is probably human myocardial adenine nucleotide translocator.