the weekend effect in aaa repair background conflicting reports exist regarding whether patients undergoing surgery on the weekend or later in the week experience worse outcomesmethods we identified patients undergoing abdominal aortic aneurysm aaa repair in the vascular quality initiative between 2009 and 2017 n 38498 30537 endovascular aneurysm repair evar and 7961 open repair we utilized mixed effects logistic regression to compare adjusted rates of perioperative mortality based on the day of repairresults tuesday was the most common day for elective repair 22 friday for symptomatic repairs 20 and ruptured aneurysms were evenly distributed patients with ruptured aneurysms experienced similar adjusted mortality whether they underwent repair during the week or on weekends transfers of ruptured aaa were more common over the weekend however patients transferred on the weekend experienced higher adjusted mortality than those transferred during the week 28 vs 21 p 002 despite the fact that during the week transferred patients actually experienced lower adjusted mortality than patients treated at the index hospital 21 vs 31 p 001 among symptomatic patients adjusted mortality was higher for those undergoing repair over the weekend than those whose surgeries were delayed until a weekday 79 vs 31 p 002 adjusted mortality in elective cases did not vary across the days of the week results were consistent between open and evar patientsconclusion we found no evidence of a weekend effect for ruptured or symptomatic aaa repair however patients with ruptured aaa transferred on the weekend experienced higher mortality than those transferred during the week suggesting a need for improvement in weekend transfer processes