We report eight patients who had a progressive illness dominated by generalised dystonia and who had clinical and imaging features suggestive of Leigh's syndrome (LS). Six of the eight cases were male. Early development was usually normal but three cases exhibited impaired mental and/or motor development, and three others had a history of an earlier unexplained encephalopathy or febrile illness. The onset of the dystonia occurred at a mean age of 3 years (range 2 months-7 years). All had abnormalities in the basal ganglia on brain imaging; symmetrical bilateral lucencies or calcification were seen in the basal ganglia on computed tomography scan in five cases, and high signal lesions were evident in these regions on T2-weighted magnetic resonance imaging sequences in seven cases. Other causes of such changes in the basal ganglia were excluded by appropriate investigations. Raised blood lactate levels were found in four of the eight patients. Muscle biopsies were done in seven patients but histology and histochemistry were normal. The common mitochondrial DNA mutations associated with LS in mitochondrial encephalopathies were not found in the six cases examined. LS presenting as a pure dystonic syndrome is uncommon, but should be considered in the differential diagnosis of symptomatic dystonia presenting in childhood.