Intensity Modulated Radiation Therapy is the most technologically advanced radiotherapy cancer treatment available. The radiation beam is modulated, and in effect focused solely on the cancer cells, allowing treatment of tumours with a higher dose, retreat cancers which have previously been irradiated, and safely treat tumours which are located very close to delicate organs like the eye, spinal cord, or rectum. This means a higher cancer control rate and a lower rate of side effects. Steve’s IMRT book published in 2000 is the principal book on the subject to date. IMRT techniques started in the 1990s and have now become the most important radiotherapy modality worldwide and are rapidly replacing earlier conformal and 3D techniques. Whilst the 2000 book remains essential as a foundation to the basics of IMRT new developments have prompted a need for a book reviewing modern applications and how IMRT is used now and into the future and captures the huge technological advances in the last 5 years.