In order to characterize the nature of mutations occurring in non-deleted Duchenne (DMD) and Becker muscular dystrophy (BMD) affected males, a total of 40 unrelated Italian patients was studied for the presence of point mutations within the muscle-specific regulatory region of the dystrophin gene. We decided to investigate the dystrophin promoter sequences because nucleotide variations in these regions could impair the expression of the gene and be the underlying molecular defect in some forms of the disease. In four patients suffering from mental retardation, the brain promoter region was also studied. To screen for point mutations, we applied molecular analysis by parallel denaturing gradient gel electrophoresis (DGGE). No sequence alterations were found in either the muscle or the brain promoters, suggesting that mutations in these regions do not represent a common mechanism of mutation in DMD/BMD.