There is evidence that autoimmunity plays a role in the pathogenesis of dilated cardiomyopathy and that susceptibility to the disease is related to products of human leukocyte antigens (HLA) class II genes. We compared the distribution of HLA-DQA1 and -DQB1 alleles and haplotypes in 44 normal controls and 34 patients with idiopathic dilated cardiomyopathy patients. The distribution of two DQA1-DQB1 haplotypes (*0102-*0604 and *0102-*0501) were more frequent in the patients. Histidine at position 30 of the HLA-DQB1 gene was associated with disease (62% of patients compared to 36% of controls), whereas homozygosity for leucine at position 26 was more frequent in controls (36% vs 18% of patients). There was no correlation between HLA-DQA1-DQB1 haplotypes and the presence of anti-beta-receptor antibodies. These results suggest that the HLA-DQB1 gene is involved in the pathogenesis of human dilated cardiomyopathy.