Purpose: Psychological distress is common among medical students. Curriculum structure and grading scales are modifiable learning environment factors that may influence student well-being. The authors sought to examine relationships among curriculum structures, grading scales, and student well-being. Method: The authors surveyed 2,056 first- and second-year medical students at seven U.S. medical schools in 2007. They used the Perceived Stress Scale, Maslach Burnout Inventory, and Medical Outcomes Study Short Form (SF-8) to measure stress, burnout, and quality of life, respectively. They measured curriculum structure using hours spent in didactic, clinical, and testing experiences. Grading scales were categorized as two categories (pass/fail) versus three or more categories (e.g., honors/pass/fail). Results: Of the 2,056 students, 1,192 (58%) responded. In multivariate analyses, students in schools using grading scales with three or more categories had higher levels of stress (beta 2.65; 95% CI 1.54-3.76, P < .0001), emotional exhaustion (beta 5.35; 95% CI 3.34-7.37, P < .0001), and depersonalization (beta 1.36; 95% CI 0.53-2.19, P = .001) and were more likely to have burnout (OR 2.17; 95% CI 1.41-3.35, P = .0005) and to have seriously considered dropping out of school (OR 2.24; 95% CI 1.54-3.27, P < .0001) compared with students in schools using pass/fail grading. There were no relationships between time spent in didactic and clinical experiences and well-being. Conclusions: How students are evaluated has a greater impact than other aspects of curriculum structure on their well-being. Curricular reform intended to enhance student well-being should incorporate pass/fail grading. Copyright © by the Association of American Medical Colleges.