This Report gives radiotherapy departments guidance on commissioning and clinically implementing intensity modulated radiation therapy (IMRT) based on established methods. It covers both inverse and forward treatment planning and optimisation, and delivery of IMRT using conventional linear accelerators with multi-leaf collimators. However the principles and processes described can be applied to other forms of delivery. The Report gives a general overview of IMRT from a clinical perspective and outlines an implementation model. Commissioning of the delivery aspects of IMRT and the treatment planning system is examined, highlighting the inter-relation between the two. Subsequent chapters cover each stage of the IMRT process including pre-treatment considerations, treatment planning and optimisation, quality assurance and treatment delivery and verification. It also explores how IMRT is developing and how it sits alongside other technological advances in radiotherapy. The Report will be of particular interest Radiotherapy Clinical Scientists and Clinical Technologists, however it does acknowledge that IMRT is a multi-disciplinary task and successful implementation requires a multi-disciplinary approach. Consequently it will also be of interest to Radiation Oncologists, Radiographers and Managers.