Four hundred and sixty records of patients with primary torsion dystonia (296 women and 164 men) were evaluated. The mean age at disease onset was 48.3 +/- 17.7 years; 13 patients carried the DYT1 CAG deletion. The distribution of age at onset was represented by a bi-modal curve, with a nadir at 21 year separating early onset from late onset cases. In 15.9% of cases there was a positive family history of dystonia. Cranial, cervical or lower limb onset was more common amongst women (M:F ratios were 1:2.7, 1:1.9, and 1:3); by contrast, onset in the upper limb was more common in men (M:F ratio 2.2:1). As expected, disease progression was more pronounced in cases with early onset; it was reckoned that onset at or above 32 years was associated with a negligible likelihood to progress to a generalized form. The mean age at onset of familial cases was 44.8 +/- 11.2 years, significantly lower than the mean age at onset of sporadic cases (53.5 +/- 13.4 years). Familial cases were characterized by more sites involved throughout disease course. Familial cases had a higher tendency to progress to a segmental or generalized form than sporadic cases.