ABSTRACT. The aim of our study was to evaluate the efficacy and safety of two concentrations of botulinum toxin A (BTX-A) for the treatment of hemifacial spasm. We randomly divided 20 patients with hemifacial spasm into high-and low-concentration groups; they were administered 50 and 25 U/mL BTX-A injection, respectively. Further, we compared the curative effects and the occurrence of adverse reactions in the two groups. Our results showed that both the concentrations of BTX-A were effective and no significant difference was observed in the onset time and therapeutic efficacy between the two groups; however, the duration of efficacy was longer in the high-concentration group than in the low-concentration group. Patients in both groups had no allergic reactions and systemic toxic reactions, but those in the highconcentration group had more serious adverse reactions and they lasted for longer durations. The adverse reactions in the two groups were not specifically treated, and they resolved in a relatively short time. In conclusion, local injection of BTX-A was effective in treating hemifacial spasm and each concentration of BTX-A had advantages and disadvantages, which indicated that the concentration of BTX-A 1137 ©FUNPEC-RP www.funpecrp.com.br Genetics and Molecular Research 14 (1): 1136-1144 (2015) Botulinum toxin A for the treatment of hemifacial spasm can be selected according to the clinical characteristics and willingness of the patients.