 This study found that approximately 3.7 billion people worldwide are at risk of financial catastrophe due to surgery. This includes 81.3 million people who are driven to financial catastrophe annually as a result of the cost of surgery alone, with another 48.5 million driven to financial catastrophe due to associated non-medical costs. The burden of catastrophic expenditure is highest in countries of low and middle income and is disproportionately borne by the poor. This article was authored by Dr Mark G. Schreim, M.D., Anna J. Dare, M.B.C.H.B., Blake C. Alkaya, M.D., and others.