Hereditary progressive dystonia with marked diurnal fluctuation (HPD) is a childhood-onset, postural dystonia that is characterized by marked diurnal fluctuation and a dramatic response to levodopa. Recently, the gene for dopa-responsive dystonia (DRD), an autosomal dominant dystonia showing similarly marked response to levodopa, has been mapped to chromosome 14q. Since HPD and DRD share many clinical characteristics, we have analyzed microsatellite polymorphisms in the region of the DRD locus and obtained a maximal lod score of 2.0 at D14S52 without obligate recombination events in the affected individuals. The results strongly suggest that HPD and DRD are to be caused by mutations in the same gene on the long arm of chromosome 14.