PURPOSE: Duchenne/Becker muscular dystrophy(DMD/BMD) is an X-linked recessive disorder caused by mutations of dystrophin genes. The purpose of the present study is to determine the frequency and the patterns of dystrophin gene deletions and to investigate the correlation of genotypes and phenotypes. METHODS: There were included a total of 89 children(88 boys and 1 girl) diagnosed as DMD/BMD by immunohistochemistry and/or genetic analysis from 1999 to 2003 at Seoul National University Children's Hospital. We analyzed the genomic DNA by multiplex PCR using a 26 dystrophin exon primer set. Direct sequencing was performed on 23 exons(in which point mutations were detected in other previous reports) in 22 patients without deletions. Phenotype and genotype relationship analysis was performed on the basis of retrospective clinical reviews. RESULTS: The frequency of dysmorphin gene deletions was 54%(32/59), which is lower than that of European and American data. Exon deletions were detected in 59 cases and the deletion "hot spots" were exon 44-54 constituting 80% of all deletions. In 6 cases without detectable deletions, 6 point mutaions(3 nonsense mutations and 3 nucleotide variants) were detected. The patients whose deletions were in the central parts or the patients with multiple exon deletions tended to show earlier symptom onsets and more rapid progressions of weakness but there were no statistical significances. CONCLUSION: Since deletions in dystrophin genes were detected in about 50% of the patients, studies on dystrophin protein expressions using muscle biopsy samples must be done for correct diagnosis.