Dilated cardiomyopathy (DCM) is defined by ventricular dilatation associated with impaired contractile function. Approximately one-third of idiopathic dilated cardiomyopathy cases are due to inherited gene mutations. Mutations in the beta- and delta-sarcoglycan genes have been described in limb girdle muscular dystrophy and/or isolated DCM. In this study, the aim was to investigate the prevalence of these genes in isolated DCM. We screened these two genes for mutations in 99 unrelated patients with sporadic or familial DCM. The coding exon and intron-exon boundaries of each gene were amplified by polymerase chain reaction. Mutation analyses were performed by single-strand conformation polymorphism for the beta-sarcoglycan gene and by direct sequencing for the delta-sarcoglycan gene. New polymorphisms, as well as already described ones, were found in these two genes, but none appeared to be responsible for dilated cardiomyopathy. We, therefore, conclude that these genes are not responsible for idiopathic isolated dilated cardiomyopathy in our population. Furthermore, based on previously published and present data, we could estimate the prevalence of delta-sarcoglycan gene mutations to be less than 1% in idiopathic dilated cardiomyopathy, demonstrating that this gene is only marginally implicated in the disease.