To evaluate brain dysfunction of childhood-onset dentatorubral-pallidoluysian atrophy (DRPLA), three children with progressive myoclonus epilepsy, who were diagnosed as having DRPLA by DNA analysis, for the first time, underwent a study of proton magnetic resonance spectroscopy (1H-MRS). 1H-MRS obtained from both the parietal and basal ganglia regions disclosed markedly reduced ratios of N-acetylaspartate to both choline and creatine. Especially regarding the basal ganglia region, the latter (ratio of N-acetylaspartate to creatine) closely correlated to severity of genetic abnormality, i.e. number of expanded CAG repeats, suggesting that the degree of neuronal loss in the region strongly depends on genetic factors. 1H-MRS must be a valuable tool to clarify the pathophysiology of DRPLA.