New molecular developments in our understanding of Duchenne and Becker muscular dystrophies are affecting the practical approach to genetic counseling, carrier detection, and prenatal prediction for these disorders. A plan of an investigation combining DNA and conventional techniques is outlined that is suitable for centers not actively engaged in molecular genetics research, based on the detection of molecular deletions, the most efficient use of multiple DNA polymorphisms, and the integration of this data with creatine kinase and pedigree information. Such an approach now allows accurate carrier detection for most women at risk as well as an acceptable degree of accuracy in prenatal detection for a proportion of carrier women.