Abstract: Objective: Allelic fragment length polymorphism analysis was performed in the family of males with Becker muscular dystrophy in one generation in order to type haplotypes among the patients, carrier and normal offspring. Methods: Deletion analysis of the patients were performed using multiplex polymerase chain reaction (PCR) of amplification with 9 dystrophin exons described by Chamberlain et al, allelic fragment length polymorphism analysis was made on DNA with PCR amplification using the intragenic short tandem repeat (STR) sequence (STR44, STR45, STR49 and STR50) in the members of the family. Results: The deletions of exons 17, 19 and 45, as well as deletions of allelic fragments at the loci of STR44, STR45 were determined in the patients, hemizygosity at those two loci were detected and carrier status ascertained in the mother of the patients. The normal haplotypes were typed in the sister of the patients.Conclusion: The method of STR sequence polymorphism analysis can determine haplotypes at normal status or at risk status, it would be used in prenatal diagnosis and carrier detection in the families of Duchenne and Becker muscular dystrophy.