Facioscapulohumeral muscular dystrophy (FSHD) is one of the most common inherited diseases of muscle. Until recently, FSHD had received little attention because of its relatively benign course and the perception that it represented a syndrome rather than a distinct myopathy. Research interest into this disease was reignited with the demonstration of linkage of FSHD to chromosome 4q35 in 1990. Clinical and molecular genetic research in FSHD has since helped define it as a distinct clinical entity, outlined its natural history, and defined the primary molecular defect associated with the condition. FSHD is now known to be associated with large deletions of variable size on chromosome 4q35. These deletions, however, do not appear to disrupt a transcribed gene but are thought to interfere with the expression of a gene or genes located proximal to the deletions. These observations complicate the search for the FSHD gene but also imply the presence of a potentially novel molecular pathogenesis.