A prospective open study of botulinum toxin A treatment for patients with various movement disorders at Siriraj Hospital, Mahidol University was analysed to evaluate its efficacy. The grand total of 900 patients comprised of a) 592 patients (65.78 per cent) with hemifacial spasm; b) 92 patients (10.22 per cent) with occupational cramp; c) 79 patients (8.78 per cent) with blepharospasm and Meige syndrome; d) 72 patients (8.00 per cent) with spasmodic torticollis; e) 19 patients (2.11 per cent) with hemidystonia and generalised dystonia; f) 11 patients (1.22 per cent) with spasmodic dysphonia; g) 10 patients (1.11 per cent) with spastic hemiparesis; and h) 25 patients (2.78 per cent) with miscellaneous group (i.e. tics, Gilles de la Tourette, facial myokimia, benign fasciculation, etc.). The results of treatment for hemifacial spasm were classified as excellent in 486 patients (82.09 per cent), moderate improvement in 60 patients (10.14 per cent), mild improvement in 39 patients (6.59 per cent) and no improvement or worse in 7 patients (1.18 per cent). There were complications of mild transient facial weakness in 50 patients (8.45 per cent) and mild ptosis in 12 patients (2.02 per cent). The effect of botulinum toxin treatment lasted 3-6 months. In occupational cramp and spasmodic torticollis the good response rate was around two-thirds of all patients, whereas, blephalospasm, spasmodic dysphonia, spastic hemiparesis and tics responsed in 79-88 per cent of the patients. Botulinum toxin A injection is thus a simple, safe, and effective out-patient treatment for patients with various kinds of movement disorders but it is a costly therapy.