The Accreditation Council for Graduate Medical Education (ACGME) in the United States limits resident physicians' workweek to 80 hours. Several studies have investigated the association between first year residents (i.e., interns, PGY1), worked hours and patient safety. This study includes residents beyond the first year (i.e., PGY2+). Nearly 5,000 PGY2+ residents reported the number of hours worked, patient safety outcomes, and resident health and outcomes. Working more than 60 hours in a week significantly increased the risk of a medical error resulting in patient death. The authors suggest weekly workweek limits should be significantly reduced, such as they are in the United Kingdom.