In this study we investigated the attitudes of Japanese medical students toward being informed of a diagnosis of life-threatening illness. Fourth-year medical students from 20 randomly sampled universities were administered questionnaires that examined their opinion about whether they would welcome disclosure of medical information if they were diagnosed as having an ultimately fatal disease. Data from 1,619 students (male 1,074, female 545, effective collection rate 90.6%) were analyzed. With regard to attitudes about disclosure of a diagnosis of life-threatening illness, 87.7% of the students stated that they would wish to be informed even if there was little chance of recovery, and 11.6% expressed a wish to be informed of their condition only if there was a chance of recovery. Students who did not wish to be informed even if there was a chance of recovery accounted for 0.7% of those surveyed. Our study reveals that medical students are more positive than are members of the general population with regard to being informed of the truth. The proportion of those who wished to be informed even if there was little chance of recovery was higher among students from national and public universities than among those from private universities, and the inter-group difference was statistically significant. Among male students, answers to the survey were significantly correlated with 12-item General Health Questionnaire scores and mental health status, suggesting that mental health status may have affected how this study population viewed being informed of their diagnosis.