To investigate dysferlin expression in muscle biopsies from patients with Duchenne muscular dystrophy (DMD). Dysferlin is known to have a role in the process of membrane fusion and muscle membrane repair in skeletal muscle fibers.We analyzed 20 muscle biopsy samples of DMD patients with immunohistochemical techniques to determine the expression of dysferlin. Immunoblotting was performed to assess dysferlin abundance in dystrophic muscle.Dysferlin showed various immunostaining patterns in dystrophic muscle, including reduced, normal, or enhanced sarcolemmal expression and intracellular immunostaining of the protein. Immunoblotting revealed that dysferlin was upregulated in 15 out of the 20 samples (75%). The abundance of the protein was analogous to the number of fibers with enhanced sarcolemmal expression of the protein.These data suggest that although dysferlin is not an integral part of the dystrophin-glycoprotein complex, its expression is altered in Duchenne muscular dystrophy.