BACKGROUND: Medical students confront significant academic, psychosocial, and existential stressors throughout their training. Mindfulness-based stress reduction (MBSR) is an educational intervention designed to improve coping skills and reduce emotional distress.PURPOSE: The purpose of this study was to examine the effectiveness of the MBSR intervention in a prospective, nonrandomized, cohort-controlled study. METHODS: Second-year students (n = 140) elected to participate in a 10-week MBSR seminar. Controls (n = 162) participated in a didactic seminar on complementary medicine. Profile of Mood States (POMS) was administered preintervention and postintervention. RESULTS: Baseline total mood disturbance (TMD) was greater in the MBSR group compared with controls (38.7 +/- 33.3 vs. 28.0 +/- 31.2; p < .01). Despite this initial difference, the MBSR group scored significantly lower in TMD at the completion of the intervention period (31.8 +/- 33.8 vs. 38.6 +/- 32.8; p < .05). Significant effects were also observed on Tension-Anxiety, Confusion-Bewilderment, Fatigue-Inertia, and Vigor-Activity subscales. CONCLUSION: MBSR may be an effective stress management intervention for medical students.