The inherited myopathies and muscular dystrophies are a diverse group of muscle diseases presenting with common complaints and physical signs: weakness, motor delay, and respiratory and bulbar dysfunction. The myopathies are caused by genetic defects in the contractile apparatus of muscle, and defined by distinctive histochemical or ultrastructural changes on muscle biopsy. The muscular dystrophies, in contrast, are diseases of muscle membrane or supporting proteins, which are generally characterized by pathological evidence of ongoing muscle degeneration and regeneration. Diagnosis of these disorders is contingent on a targeted history and examination, biochemical and neurophysiological assessment, muscle biopsy, and genetic testing. Treatment is focused on symptomatic management and rehabilitation, and monitoring for disease complications.