The separation of the masticator and parapharyngeal spaces is somewhat ambiguous. Anatomic specimens were dissected to define better the fascial layer representing the medial wall of the masticator space. A fascial layer was found extending from the medial pterygoid muscle to the skull base separating the masticator from the parapharyngeal space. The third branch of the trigeminal nerve was lateral to this fascial layer and thus passed through the masticator space. Clinical cases were reviewed. Tumors could be confidently assigned to the masticator, prestyloid, or poststyloid parapharyngeal spaces. Benign salivary gland tumors were found in the prestyloid parapharyngeal space only.