The majority of studies on the effects of botulinum toxin in blepharospasm patients have been small or unblinded. Our large-scale, multicenter, randomized clinical trial on the efficacy and safety of botulinum toxin (Dysport; 40, 80, and 120 units/eye) versus placebo in bilateral benign essential blepharospasm (BEB) supported the high efficacy and good safety profile of Dysport, with improvement in functional impairment, reduced frequency and intensity of facial spasms, and fewer withdrawals through lack of efficacy in the active treatment group compared with controls. The best balance of sustained efficacy and favorable safety profile was provided by 80 units of Dysport/eye in this study.