Abstract: Detaching the lateral pterygoid muscle from the mandible is one of the methods in the treatment of lesions of the temporomandibular joint.According to Burke’s report, the success of the lateral pterygoid myotomy may be due to postsurgical scarring,with subsequent limitation of motion,rather than through the detachment and ultimate loss of function of the lateral pterygoid muscle.This procedure may be not justified because of secondary morphological changes.The surgical injury is directly affection the joint itself and the pathologic changes of the joint can not be avoided. This paper presents a new method which was proposed by Dr.Hong Min,one ol the anthors,to treat lesions of the T.M.J.,that is detaching the lateral pterygoid muscle from the lateral pterygoid plate intra-orally.Because the operation is performed far away from the joint,any injury to the joint can be prevented. 50 patients underwent this type of treatment druing the period from 1976-1982 with successful results.24 patients were reviewed 1/2 to 1 year after operation.Over-all results were good in 20,and fair in 4.No patient was made worse. In this paper,the method of operation was described and discussed.