Although the vast majority (about 70%) of patients with cancer will have pain directly related to neoplastic invasion into pain-sensitive bone and soft tissue structures,as many as 20% of the adults will have pain caused directly by cancer therapy. Treatment related pain problems are important for several reasons; their appearance may be confused with more omnious pain syndromes associated with tumor recurrence or progression that may be directly lead to death of the patient; when severe, compliance with recommandations for further therapy may be adversely affected. Now, we report a case of postsurgical pain syndrome after radical neck dissection in a patient with tonsilar cancer. The pain after radical neck dissection result from injury to the cervical plexus,cranial nerve,and cervical sympathetics. In our case, we ruled out soft tissue infection and tumor recurrence,and successfully treated with gasserian ganglion block with pure alcohol in the patient having neuropathic pain in the mandible and preauricular region after radical neck dissection.