Purpose: Little is known about students who seriously consider dropping out of medical school. The authors assessed the severity of thoughts of dropping out and explored the relationship of such thoughts with burnout and other indicators of distress. Method: The authors surveyed medical students attending five medical schools in 2006 and 2007 (prospective cohort) and included two additional medical schools in 2007 (cross-sectional cohort). The survey included questions about thoughts of dropping out, life events in the previous 12 months, and validated instruments evaluating burnout, depression symptoms, and quality of life (QOL). Results: Data were provided by 858 (65%) students in the prospective cohort and 2,248 (52%) in the cross-sectional cohort. Of 2,222 respondents, 243 (11%) indicated having serious thoughts of dropping out within the last year. Burnout (P < .0001), QOL (P < .003 each domain), and depressive symptoms (P < .0001) at baseline predicted serious thoughts of dropping out during the following year. Each one-point increase in emotional exhaustion and depersonalization score and one-point decrease in personal accomplishment score at baseline was associated with a 7% increase in the odds of serious thoughts of dropping out during the following year. On subsequent confirmatory multivariable analysis, low scores for personal accomplishment, lower mental and physical QOL, and having children were independent predictors of students having serious thoughts of dropping out during the following year. Conclusions: Approximately 11% of students have serious thoughts of dropping out of medical school each year. Burnout seems to be associated with increased likelihood of serious thoughts of dropping out.