Phenomenon: Little is known about how participation in disaster relief impacts medical students. During the terror attacks of September 11, 2001, New York Medical College School of Medicine students witnessed the attacks and then became members of emergency treatment teams at St. Vincent's Hospital, the trauma center nearest to the World Trade Center. To date, only two reports describe how 9/11 influenced the lives of medical students. This study was designed to characterize the short- and long-term effects on NYMC students and to compare those effects between students assigned to St Vincent's Hospital and classmates assigned to rotations at facilities more remote from the attack site. We hypothesized that participation in direct relief efforts by students assigned to the St. Vincent's site might have long-lasting effects on their lives and these effects might vary when compared to classmates assigned elsewhere. Approach: This was a retrospective, survey-based, unmatched cohort study. Participants included all school of medicine graduates who were St. Vincent's rotators on 9/11 (N = 22) and classmates (N = 24) assigned to other sites who could be contacted and agreed to participate. Our primary measure was whether the 9/11 experience affected the participant's life, defined as an affirmative response to the item which asked whether the 9/11 experience affected the participant's "life thereafter, career choice, attitudes toward life or attitudes toward practice." Secondary measures included self-reported effects on career, life, attitudes, health, resilience, personal growth, personality features, and the temporal relationship between the attack and stress symptoms. Findings: Completed surveys were received from 16/22 (73%) St. Vincent's and 18/24 (75%) non-Saint Vincent's participants: 62% male, 82% had children, 74% identified as Caucasian/white and 76% employed full-time. Overall, slightly more than half (58%) of respondents reported an effect of 9/11 on their life, with a greater but non-significant proportion of St. Vincent's rotators reporting life impact (67% versus 50% for St. Vincent's versus other locations, respectively). High post-9/11 stress levels, current marriage, and ability to make and keep family and social relationships were associated with an effect on life which approached statistical significance. Participants reported positive or no post 9/11 effects on empathy and altruism (50%), resilience (47%), attitudes toward medical practice and career (32%), and charitable giving (24%), while positive, negative, or no effects were reported for attitude toward life, family and social relations, physical health, and conscientiousness. Mental health was the only domain in which all participants reported unchanged or negative effects. Two St. Vincent's rotators but no students assigned elsewhere believed they experienced 9/11-related post-traumatic stress disorder. Insights: Just over half of New York Medical College School of Medicine students rotating at St. Vincent's Hospital on 9/11 or elsewhere reported significant life-effects as a result of direct/indirect experiences related to the attack. Perceived stress may have been a more important driver of this life-change than other factors such as geographic proximity to the disaster site and/or direct participation in relief efforts. Further study of medical school interventions focused on stress reduction among students who participate in disaster relief is warranted.