Dystrophin is a protein that provides muscle fiber stability during exercise by linking the actin cytoskeleton to the extracellular matrix. Duchenne muscular dystrophy (DMD) is caused by frame-shifting mutations that prevent the production of functional dystrophin protein. By contrast, Becker muscular dystrophy is caused by mutations that maintain the open reading frame and allow the production of an internally deleted, partially functional dystrophin protein. DMD has an early onset and is characterized by a severe disease progression, leading to wheelchair-dependency before the age of 12 and death in the 2nd-4thdecade of life. BMD is more variable, but generally the onset is later and the disease progression slower than for DMD patients. The rationale of the exon skipping approach is to modulate pre-mRNA splicing of dystrophin transcripts to restore the reading frame and allow DMD patients to produce BMD-like dystrophins. Exon skipping is achieved with small modified pieces of DNA (antisense oligonucleotides) that bind specifically to the target exon and hide it from the splicing machinery. The thesis describes optimization of antisense oligonucleotides in muscle cell cultures, proof-of-concept studies of antisense-mediated exon skipping in patient-derived cell cultures, showing exon skipping and dystrophin restoration and proof-of-concept studies of exon skipping in animal models.