The genes for six forms of recessive muscular dystrophy have so far been identified, although more are certain to be revealed. Differential diagnosis on clinical grounds alone can be very difficult, so a classification system based on the underlying molecular defect has been introduced. Muscle biopsies are taken for routine diagnostic histopathology, and the various proteins implicated in muscular dystrophy can be analysed immunologically and the results used to indicate where to start searching for gene mutations. A flow diagram is presented which demonstrates how such protein analysis could be optimized.