The relationship between HCV (hepatitis C virus) and the susceptibility of cardiomyopathy has been indicated, but the detailed mechanism for close association is still unknown. It is well known that the human leukocyte antigen (HLA) may regulate the development of chronic hepatitis in HCV positive patients. We have analyzed the distribution of HLA class II alleles in Japanese patients with HCV antibody positive dilated cardiomyopathy (DCM) and hypertrophic cardiomyopathy (HCM), and HLA-DPB1*0901 was significantly increased in HCV Ab positive DCM, and the HLA-DRB1*0901-DQB1*0303 haplotype was in HCV Ab positive HCM. These results suggested that molecular mechanism for the development of cardiomyopathy mediated by HCV is different between DCM and HCM.