Analysis of Bulgarian Duchenne/Becker muscular dystrophy (DMD/BMD) patients has demonstrated that deletions spanning exon 4 or exon 48 of the dystrophin gene account for about half of all patients, and that female relatives from these families constitute nearly 40% of all patients who require diagnosis of carrier status. We propose a relatively simple and inexpensive assay for the detection of deletion carriers based on a duplex PCR with radioactive 5' end labeling of one of the PCR primers for each exon. The PCR amplification is performed under conditions of exponential relationship between template DNA and the amount of PCR product obtained, thus facilitating gene dosage. The quantification of the products, and especially the use of a coefficient estimating of the relative proportion of each exon in the total densitometric area, provide a reliable differentiation between carriers and non-carriers.