A case of familial paroxysmal dystonic choreoathetosis (PDC) documented by video/EEG monitoring is described. The father of the proband is affected by exertional cramping but not PDC, lending support to the previous hypothesis that exertional cramping may represent a "forme fruste" or the incomplete expression of PDC. Other family members affected by PDC are women, with exercise-induced cramping alone found in two men. Two of the women report prolonged exertion as a precipitant of lengthy spells consistent with typical PDC rather than the previously described "intermediate," exercise-induced form of PDC. Exertional cramping in families affected by PDC may represent the variable expression of the "dystonia gene" in male members. Conversely, exercise-induced PDC, both of the intermediate and longer form described here, may have a predilection to manifest in women.