The occurrence of muscular atrophy in multiple sclerosis (MS) has been considered unusual and classically has been ascribed to disease involving the motor unit. Nine patients with MS in a single clinic were found by strict criteria to have focal hand muscle atrophy associated with weakness. None had electrodiagnostic evidence of either anterior horn cell or axonal abnormalities. These observations indicate that focal muscular atrophy is common in MS; it may often occur as a result of relative disuse resulting from disease of central pathways involved in motor control.