The use of antisense oligonucleotides (AOs) to induce exon skipping leading to generation of an in-frame dystrophin protein product could be of benefit in around 70% of Duchenne muscular dystrophy patients. We describe the use of hyaluronidase enhanced electrotransfer to deliver uncomplexed 2'-O-methyl modified phosphorothioate AO to adult dystrophic mouse muscle, resulting in dystrophin expression in 20-30% of fibres in tibialis anterior muscle after a single injection. Although expression was transient, many of the corrected fibres initially showed levels of dystrophin expression well above the 20% of endogenous previously shown to be necessary for phenotypic correction of the dystrophic phenotype. (C) 2003 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.