The seminal report, To Err Is Human, famously estimated that 44,000 to 98,000 deaths per year in the United States were due to medical errors. Although certain patient harms thought to be unavoidable at the time of the report's publication in 1999 are now considered completely preventable, experts suggest that progress in the field of patient safety has been slower than initially anticipated and that areas such as ambulatory safety and diagnostic error represent emerging priorities. In this cohort study, researchers used data from 1990 through 2016 on mortality related to the adverse effects of medical treatment (AEMT) from the Global Burden of Diseases, Injuries, and Risk Factors 2016 study. For the study period, researchers attribute 123,603 deaths to AEMT. The number of such deaths increased, but the US age-standardized mortality rate for deaths due to AEMT decreased by 21% between 1990 and 2016. The authors noted similar AEMT mortality rates for men as compared to women, significantly increased AEMT mortality rates for those age 70 and older, and geographic variation with regard to age-standardized AEMT mortality rates. An Annual Perspective discussed challenges associated with measuring and responding to deaths associated with medical errors.