The Purpose of this study is to report the effect botulinum toxin type A injection for the masseter hypertrophy patient with bruxism. Nine patients enrolled in this study were diagnosed as masseter hypertrophy associated with bruxism and the patients were injected with a 25U of botulinum toxin type A (BTXA:Lanzhou) to each masseter muscles. All nine patients showed marked reduction of masseter hypertrophy and eight patients reported the resolution of bruxism in 8 weeks after injection, with no significant complications. This preliminary study suggest that the botulinum toxin type A injection is an alternative method to treat the masseter hypertrophy with bruxism.