Duchenne muscular dystrophy (DMD) has been a major target for gene therapy development for nearly 30 years. DMD is among the most common genetic diseases, and isolation of the defective gene (DMD, or dystrophin) was a landmark discovery, as it was the first time a human disease gene had been cloned without knowledge of the protein product. Despite tremendous obstacles, including the enormous size of the gene and the large volume of muscle tissue in the human body, efforts to devise a treatment based on gene replacement have advanced steadily through the combined efforts of dozens of labs and patient advocacy groups. Progress in the development of DMD gene therapy has been well documented in Molecular Therapy over the past 20 years and will be reviewed here to highlight prospects for success in the imminent human clinical trials planned by several groups.