We reviewed the records of all patients with paroxysmal nonkinesigenic dystonia seen at Dystonia Clinical Research Center. Of the total of 25 patients, three subgroups based on etiology were discerned: primary sporadic (7 patients), psychogenic (11 patients), and symptomatic (7 patients). There were no patients with primary paroxysmal dystonia with a family history of a similar disorder. Although many of the characteristics of our sporadic cases were similar to those of familial paroxysmal dystonia reported in the literature, numerous differences were noted including adult onset, female predominance, and variability in the duration and frequency of attacks. In certain cases an overlap with PKC was found. Clonazepam and acetazolamide were effective in several patients.