Abstract : Muscular temporomandibular disorders are a common pain problem that requires treatment because of its symptoms of pain, poor function, and limited mouth opening in a way that affects the individual’s daily activity. Botox is mainly used to treat muscular temporomandibular joint disorders and hyperactivity of the masseter muscles. The aim of the study was to improve the maximum mouth opening in patients with muscular TMD using EMG-guided Botox injection into the masseter and lateral pterygoid muscles. A randomized clinical study was conducted on 18 patients diagnosed with TMJ disorders of muscular origin, who were randomly divided into two equal groups: the first group (A) received bilateral injection of botulinum-A toxin into the masseter and lateral pterygoid muscle, and the second group (B) administered bilateral injection of botulinum-A toxin into the masseter muscle only. mouth opening was measured before, two weeks, six weeks, three months, and six months after treatment. The results showed a significant improvement in mouth opening when botulinum toxin was injected into the masseter and lateral pterygoid muscles during a follow-up period of 6 months.