Purpose: With increased use of imaging studies raising the detection rate of abdominal aortic aneurysms (AAAs), more surgeons must make decisions about the timing of elective surgery during watchful waiting (WW) for patients with asymptomatic, expanding AAA. AAA have an average annual expansion range 0.2 - 0.4 cm with a constantly increasing risk of a fatal rupture. Opposing this risk is the 5% mortality rate associated with elective surgery. Statistically-based guidelines advocate delaying surgery until the risk of an AAA rupture (at 5.5cm) surpasses that for surgical mortality, but it is not clear that surgeons strictly follow these guidelines, and it is possible that preceding patient outcomes alter decisions. Methods: This field experiment presented surgeons with a computer simulation that required managing a hypothetical asymptomatic patient with an expanding AAA. Surgeons decided between continuing WW, as the AAA expanded, or going to surgery and accepting the 5% morality risk. With each decision to continue WW, the simulation updated the AAA size and rupture risk probabilities. Surgeons first performed a practice round of the simulation that randomly presented them with a WW rupture, a surgical fatality, or no bad outcome. The dependent variable was the number of times surgeons continued WW. Additionally, surgeons answered survey questions measuring anxiety, risk attitudes, and intolerance for uncertainty, demographic information, surgical experience, and self-reported decision strategy. A Cox-regression analysis, for the event of going to surgery, was conducted. Results: Surgeons (n=66) at a national conference, of which 68% indicated having surgical experience with AAA, participated in the study. Cox-regression survival analysis results showed a significant effect for the manipulation (Wald = 7.9, p < .02) where participants in the WW rupture condition were 2.6 times more likely to go to surgery (HR = 2.59, p <.05). There was a trend for those in the bad surgical outcome condition to wait longer, but it was not statistically-significant. Conclusions: Previous experience of AAA ruptures can expedite surgeons' choice for surgery, even when they are provided with updated statistical guidelines to inform their decisions. Additionally, there was a trend towards previous experience of a simulated surgical fatality prolonging WW. These results suggest that previous patient outcomes can independently influence the decisions made by professional surgeons, even when statistical guidelines are immediately present.