The distal part of the human dystrophin gene is characterised by particular features and seems to play an important functional role. Additionally in recent years several data have implicated minor mutations in this gene region in some patients with mental retardation (MR). In order to screen for pathogenic mutations at the distal part of the human dystrophin gene we have used single-strand conformation analysis of products amplified by polymerase chain reaction (PCR-SSCA) in 35 unrelated male Greek DMD/BMD patients with no detectable deletions. Seven patients also had severe mental retardation. Direct sequencing of samples demonstrating a shift of SSCA mobility revealed six different and pathogenic minor changes, five in DMD and one in a BMD patient. Four of the mutations were found in DMD patients with severe MR. Three of these mutations were localised in exon 66, which presents an interesting similarity with part of the 3' end of the genome of eastern equine encephalomyelitis virus (EEEV). The present data from Greek DMD/BMD patients give further information about the phenotypic effects consequent on mutations in exons at the distal part of the human dystrophin gene.