Doctors in different countries have different approaches to bioethical problems. We studied how attitudes to life-sustaining treatment for terminally ill patients differ in Japan and the USA by administering a questionnaire to Japanese (136) and Japanese-American (77) physicians. In a series of clinical scenarios the questionnaire asked what life-sustaining interventions the doctors would recommend to a patient with metastatic gastric cancer. Most Japanese physicians would recommend blood transfusions for gastrointestinal bleeding (74%), total parenteral nutrition for malnutrition (67%), and vasopressors for life-threatening hypotension (61%) when the patient did not know of his diagnosis and outlook. Significantly fewer Japanese physicians would want these interventions for themselves: 29% would want transfusion, 36% would want total parenteral nutrition, and 25% would want vasopressors. 36% of Japanese physicians would override the explicit request of a competent moribund cancer patient to withdraw all life-support. By contrast, among Japanese-American physicians only 42% would recommend blood transfusions, 33% total parenteral nutrition, and 34% vasopressors to a terminally ill cancer patient who did not know of his diagnosis or outlook. Cross-cultural studies in medical ethics can help physicians and the public in different countries to take a fresh look at accepted practices and the ethical reasons behind them.