Over the last few years it has become clear that a proportion of biopsies from patients with Duchenne muscular dystrophy (DMD) contain fibres which show dystrophin-positive immunolabelling. We have collected evidence to demonstrate that low level restoration of the reading frame must have been taking place and that a BMD-like protein was being synthesized in DMD muscle. We have also found a relationship between the abundance of dystrophin (determined by densitometric analysis of blots) and the age at which boys lose the ability to walk independently. Thus, even the low levels of dystrophin in DMD patients may have a functional significance. We now suggest that exon skipping, whereby an existing frame-shifting deletion is modified and extended to an in-frame mutation, may be responsible for the limited rescue of dystrophin synthesis in the muscle from many DMD patients.