A 45-year-old woman with a history of probable perinatal craniocerebral trauma resulting in mild asymptomatic right hemiatrophy developed right leg weakness and hypotonia alternating with dystonia only after prolonged exertion at age 12. At age 27, she developed right-sided parkinsonism. Exertional paresis and dystonia and parkinsonism responded completely to levodopa; however, she developed a progressive reduction in the duration of action of levodopa over the first 4 years of treatment. Investigations including computed tomography, magnetic resonance imaging, [18F]fluorodopa, and [18F]fluorodeoxyglucose positron emission tomography scans suggested a static lesion involving the left substantia nigra. This unusual exertion-induced weakness and hypotonia alternating with hypertonia and dystonia has not been reported previously. The role of dopamine deficiency in dystonia and the role of levodopa in the development of fluctuations in Parkinson's disease are discussed. Review of the literature, including this patient, emphasizes the heterogeneity of the syndrome of hemiparkinsonism-hemiatrophy.