Transcranial magnetic stimulation has been used in the diagnosis of neurological lesions, but has also been shown to be useful in the treatment of depression. We have now examined the effect of applying transcranial magnetic stimulation daily for 10 days in a sample of 10 patients with Parkinson's disease in whom maximal benefit was being obtained from drug therapy. The subjects were followed for six months and showed significant improvements over this period when assessed using a range of measures. It is suggested that transcranial magnetic stimulation may be a valuable technique in the treatment or adjunct treatment of Parkinsonism, possibly by inducing changes in brain monoamine levels.