A themed collection from The Lancet, dedicated to traumatic injury and surgery. The first Article presents new estimates of death following general surgery. The Europe-wide study finds death rates after surgery are double that of previous estimates. According to the second Article, survival after a general anaesthetic and within 48 hours of surgery has greatly improved worldwide over the past 50 years. An accompanying Comment calls for application of effective perioperative practices to under-resourced settings. New research published in the third Article on surgery suggests that the millions of intravenous catheters used each year can be safely changed only when clinically necessary, overturning 40 years of accepted practice. Also in this collection, a three-part series on trauma surgery reviews recent progress and challenges in the management of acute trauma care in haemorrhagic shock, traumatic brain injury, and major musculoskeletal injury. The Series not only reveals progress in the understanding of genomic, proteomic, and physiological changes related to severe injury and of the response to resuscitation and surgery, but also presents global initiatives to address shortcomings in previous approaches to trauma research. An associated Comment urges for research so that "injured people can benefit from the sorts of research-based advances that have transformed other fields of healthcare". The Lancet commissions Series and themed issues to highlight clinically important topics and areas of health and medicine that are pertinent to physicians’ practice. They are groups of two or three articles which provide pathophysiology, basic science, and genomic insights, as well as practical, up-to-date clinical information on a variety of important or neglected disorders.