Summary: The U.S. health care system has been criticized for encouraging the "overuse" of the newest and most costly medical treatments. This report examines the use of one complex, expensive, high-technology medical treatment--allogeneic bone marrow transplantation--in the United States and in nine foreign countries: Australia, Canada, Denmark, France, Germany, the Netherlands, New Zealand, Sweden, and the United Kingdom. During this procedure, which can cost upwards of $125,000 in the United States, the patient's bone marrow is destroyed and replaced with marrow from a healthy donor. GAO found that U.S. leukemia patients were less likely than those in six of the foreign countries to receive bone marrow transplants in time to potentially cure them. Although U.S. doctors perform the operation about as frequently as those in other industrialized nations, they often wait until the disease is more advanced and the patient's chances for recovery are less promising. These findings challenge the assumption that the United States relies more than other medically advanced nations on new and complex treatments. U.S. patients, for good or ill, have not been the most likely to receive a transplant for any of the clinical conditions examined.