The authors measured factors associated with under-treatment of medical students' depression. They administered a cross-sectional Beck Depression Inventory and sociodemographic questionnaire to students at 1 medical school, defining their outcome measure as the use of counseling services or antidepressant medication. Of an estimated 450 available student participants in the study, 322 (71.6%) completed the questionnaire. Forty-nine students (15.2%) were classified as depressed and 10 (20.4%) reported experiencing suicidal ideation during medical school, but only 13 (26.5%) of the depressed students reported treatment. The researchers observed no difference in treatment by year in school, completion of psychiatric requirement, race, or depression severity. Treatment for depression was significantly associated with older age and personal and family histories of depression. Despite the availability of effective medications and confidential mental health services, medical students with depression are undertreated. The authors' findings support the need for targeted messages to help medical students recognize their depression and refer themselves for appropriate treatment.