Recently, mutations in the genes encoding several of the dystrophin-associated proteins have been identified that produce phenotypes ranging from severe Duchenne-like autosomal recessive muscular dystrophy to the milder limb-girdle muscular dystrophies (LGMDs). LGMD type 2C is generally associated with a more severe clinical course and is prevalent in northern Africa. A previous study identified a single base pair deletion in the gene encoding the dys-trophin-associated protein γ-sarcoglycan in a number of Tunisian muscular dystrophy patients. To investigate whether γ-sarcoglycan gene mutations cause autosomal recessive muscular dystrophy in other populations, we studied 50 muscular dystrophy patients from the United States and Italy. The muscle biopsies from these 50 patients showed no abnormality of dystrophin but did show diminished immunostaining for the dystrophin-associated protein α-sarcoglycan. Four patients with a severe muscular dystrophy phenotype were identified with homozygous, frameshifting mutations in γ-sarcoglycan. Two of the four have microdele-tions that disrupt the distal carboxyl-terminus of γ-sarcoglycan yet result in a complete absence of γ- and β-sarcoglycan suggesting the importance of this region for stability of the sarcoglycan complex. This region of γ-sarcoglycan, like β-sarcoglycan, has a number of cysteine residues similar to those in epidermal growth factor cysteine-rich regions.