We studied the effects of botulinum A toxin in 101 patients with hemifacial spasm and 11 patients with blepharospasm in an open trial and double blind manner. All patients in the open trial and 6 patients in the double blind trial improved after the first injection of botulinum toxin. There was no improvement with placebo. The peak effect ranged from one to 6 days after injection and mean peak effect was 3.6 days in blepharospasm, and 4 days in hemifacial spasm. Of 144 treatments, 98.6% had excellent results, (below grade I). The duration of beneficial effect ranged 11 to 40 weeks (mean 16.5 weeks) in hemifacial spasm and 9 to 30 weeks (mean 14.2 weeks) in blepharospasm. Complications were encountered in 63.4% in hemifacial spasm and 72.7% in blepharospasm. The common side effects were dry eyes, mouth droop, ptosis and lid edema in order of frequency. These side effects were mild and resolved spontaneously in 1 to 3 weeks. Botulinum A toxin therapy is effective and convenient, and the treatment of choice for patients with hemifacial spasm and blepharospasm.