How many patients die each year due to preventable adverse events is difficult to determine. Early studies summarized in the seminal To Err Is Human report yielded an estimate of 44,000 to 98,000 deaths due to errors yearly. More recent studies have challenged that estimate. A recent British study found that only 3.6% of inpatient deaths were potentially avoidable, which translates to approximately 26,000 preventable deaths each year in the United States. This commentary argues that preventable deaths total more than 250,000 deaths per year, which would rank medical errors as the third most common cause of death. This estimation was developed by extrapolating preventable death rates from several studies with different methodologies to estimate avoidable adverse events; no formal meta-analysis was performed. It is important to note that discerning the preventability of adverse events (and consequent deaths) is difficult. Most studies of preventable harm find that even experienced clinical reviewers achieve only moderate interrater agreement on whether an adverse event occurred and, if so, whether it contributed to death. Although this article's estimate is likely to be controversial, the authors do highlight the lack of accurate strategies for measuring safety events—a problem also highlighted in a recent commentary by two patient safety leaders. Regardless of the exact number, too many patients die needlessly due to unsafe care.