A search for female mutation carriers was performed in 40 families with an isolated case of Duchenne/Becker muscular dystrophy due to a deletion in the dystrophin gene. Intragenic restriction sites and microsatellite sequences (CA repeats) were analysed in females possible carriers of the deletion. Application of this approach enabled us the detection of the deletion in 19 females in 9 families and exclusion of the deletion in 41 females in 23 families. The results of DNA analysis in the remaining 8 families were not informative.