Estimating carrier risks for female relatives of Duchenne (DMD) and Becker (BMD) dystrophy sufferers depends upon calculation of segregational risks, supplemented by enzyme tests which show considerable overlap between carrier and control data. Linkage analysis has substantially increased the accuracy of segregational risk estimation, but a small error rate is still inherent when interpreting results, owing to recombination between the mutation causing the disease, and the marker used. It also requires family studies, which may be difficult to complete. The presence of intragenic DNA deletions in about half of D/BMD boys, allows direct detection of the D/BMD mutation, and is a powerful diagnostic tool. These techniques can be used for both prenatal diagnosis and carrier detection.