The potential usefulness of viral gene replacement therapy in human disease has been an exciting and extensively-studied topic in the field of skeletal muscle disease for the past 20 years. Unfortunately, while the strategy of replacing or supplementing copies of mutant gene is a straightforward concept, a number of complicating factors have been identified as gene therapy trials have progressed toward clinical studies. While some of these issues, including the immunological response to viral vectors, are issues that are encountered with all forms of gene therapy, the use of gene therapy in skeletal muscle also poses additional challenges for which treatment strategies need to be optimized. Despite these challenges, there has been substantial progress in recent years toward optimizing viral gene therapy for skeletal muscle disease in animal models, with an eye toward optimizing the safety and efficacy of viral gene therapy in humans. Skeletal muscle disorders represent considerable opportunities for investigators developing viral gene therapy strategies, due to the numerous monogenetic diseases of skeletal muscle, the clear and quantifiable clinical phenotypes, and the easy accessibility of muscle tissue. Mutations in the dystrophin gene predispose the myofiber membrane to contraction-induced membrane damage, resulting in inflammation, and myonecrosis, and progressive loss of functional muscle tissue. Several murine and canine models of dystrophinopathy have been used to study these diseases and evaluate potential therapies, including several viral gene therapy approaches. Viral gene therapy approaches have also been investigated for other disorders of skeletal muscle, including lysosomal storage disorders and congenital myopathies, and these studies have benefitted immensely from the pioneering work that was performed using dystrophinopathy models. (Michael W. Lawlor, Viral Gene Therapy in Skeletal Muscle: A Work in Progress).