The Companion is a distillation of clinical material from Principles. In the words of the editors, It has been written with easy reference to the full text of HPIM and it is recommended that the full textbook be consulted as soon as time permits. Thus, we consider HPIM and the Companion Handbook as a combination that is complementary, but not interchangeable. The new edition includes all the material included in HPIM15. In addition, a larger trim size will allow the inclusion of 25-30% more material. This will include longer sections on the approach to the patient and treatment, more figures and tables and evidence-based medicine summaries. The Companion does not include the detailed pathophysiology found in HPIM and all clinical sections have been abbreviated. Bullets and lists are used wherever possible.