The gross tumour volumes of both the primary tumour (GTV-P) and the radiologically involved cervical nodes (GTV-N) are outlined on the planning CT images with the aid of co-registered MRI images. Subsequently clinical target volume (CTV-70) and planning target volume containing CTV-70 with a 3mm margin (PTV-70) are generated to take into account the microscopic disease spread, physiological body motions and set-up errors respectively. Another CTV-66 encompassing the high risk areas including the posterior half of the maxillary sinuses, nasal cavities, parapharyngeal spaces, styloid processes, basi-occiput, basi-sphenoid, clivus, foramina rotunda and ovale, pterygopalatine fossae, pterygomaxillary fissures, infra-orbital fissures, cavernous sinuses and level Ib and level V nodal stations is also contoured. A corresponding PTV-66 with a 3mm margin encompassing CTV-66 is created by boolean operations of the treatment planning system which is also used for IMRT optimization and planning. All OARs including brainstem, spinal cord, globes, optic nerves, optic chiasm, lenses, temporomandibular joints, temporal lobes, auditory nerves, cochleae, mandible, oral cavity, larynx, parotid glands, vestibules, pituitary and thyroid are to be contoured manually. During IMRT optimization, the maximum dose of brainstem, optic nerves and chiasm must be <=54 Gy (allowing 0.1cc brainstem <60 Gy) and spinal cord <=45 Gy (allowing 0.1cc spinal cord <48 Gy). Efforts will also made to limit mean dose of parotid glands to 26 Gy whenever possible and dose to the lenses and temporal lobes as low as reasonably achieved without compromising dose coverage to the PTVs. No dose constraint is to be given to the thyroid and pituitary during optimization of all IMRT plans.