One hundred and one patients with idiopathic blepharospasm have been treated with injections of botulinum toxin A into the orbicularis oculi. Ten had previously had facial nerve avulsions and responded well, normal visual function being restored in the majority (7/10) for an average of 14 weeks. Without prior surgical treatment the response was more variable, but 71/91 regained normal or near normal vision. Older patients, those with a family history of the condition, and those without oromandibular dystonia responded slightly better. The severity of the blepharospasm, the length of the history, and spontaneous resolution of an episode of focal dystonia in the past had no influence on the outcome. Results were poor in the presence of an associated neurological disorder. Side effects, particularly a temporary partial ptosis, were common but were well tolerated. The average duration of improvement was eight weeks in men, nine in women, and there was no evidence of any increase in duration after multiple injections. Eighty nine patients continued with injections, 11 opted for surgical treatment, and one resumed drugs.