A family with a syndrome of mental retardation, dystonic movements of the hands, and dysarthria (MIM no. 309510) was described and mapped to Xp22 by Partington et al. (Am J Med Genet 1988; 30:251-262). The original localization encompassed the distal half of the short arm of the X chromosome, with a peak lod score of 2.1 at the DXS41 locus. The gene localization for this disorder (PRTS) has now been refined using recently characterized dinucleotide repeat markers. The PRTS gene maps between DXS365 and DXS28, an interval estimated to be less than 15 cM. A peak lod score of 3.01 at a recombination fraction of zero was generated by 2-point linkage analysis with the marker DXS989. Dystonic movements may be progressive and could be overlooked in children. Clinical assessments of affected men who are mentally retarded should be critically evaluated for this manifestation, where they belong to families in which the gene localization overlaps with PRTS.