We reviewed the histories of 115 patients who had idiopathic dystonia and who were 21 years of age and younger at onset of symptoms and 472 patients with onset older than age 21. Patients with onset in the lower extremities tended to be younger at onset (mean age 8.4 years), have rapid spread of symptoms to other body parts, and to develop generalized dystonia. Patients with onset in the upper extremities tended to be older at onset (mean age 11.2 years) and were less likely to develop generalized dystonia, but were more likely to experience spread of symptoms many years after the disease began. Almost 20% of patients younger than age 22 began with torticollis, and 67% of these remained focal after a mean 14.9 years. In adults, dystonic symptoms remained focal in the majority, but approximately 15-30% of patients presenting with blepharospasm, torticollis, laryngeal or brachial dystonia eventually experienced dystonia outside the initially involved segment. Almost 50% of children and adolescents with dystonia reported a family history of dystonia, compared with approximately 10-13% of patients with torticollis, laryngeal or brachial dystonia. Less than 3% of patients with blepharospasm reported a family history of dystonia. There were only minor differences in the pattern of spread of dystonic symptoms between Jewish and non-Jewish patients. Although younger patients were more likely to report a family history of dystonia, patterns of spread were the same for familial and sporadic patients in the same age range.