We have examined 29 subjects with writers' cramp (and 4 with typists' and one with pianists' cramp) and have noted two major groupings, simple and dystonic. We have observed spread from one to the other. We have seen repeatedly, in patients with isolated simple writers' cramp certain subtle physical signs which are found also in other basal ganglia diseases. We have noted also the frequent association of other features of segmental and generalized dystonia in patients with dystonic writers' cramp. We have demonstrated that patients with isolated writers' cramp have no higher an incidence of psychiatric disturbance, as judged by formal Present State Examination, than the normal population. We conclude that isolated writers' cramp is a physical illness rather than a psychological disturbance, and that it is a focal dystonia.