Medical malpractice claims and dispute resolution systems have been examined in Western societies for their impact on the quality of care and efficient compensation for injured patients. However, little is known about the Japanese malpractice environment because claim information has been closely guarded. Based on data from the Japanese Supreme Court, the Ministry of Health, Labor, and Welfare (formerly the Ministry of Health and Welfare), and the Japan Medical Association (JMA), which provides malpractice insurance to 43.5% of Japan's 250 000 physicians, we review Japanese malpractice liability systems and the frequency of claims during the last 30 years. Annual premiums for physician professional liability insurance are relatively low (454 dollars-491 dollars). Although the frequency of claims in Japan is lower than that reported in the United States, England, and Germany, the number of claims is increasing in Japan. According to publicly available data from the Japanese Supreme Court, the annual number of medical malpractice suits filed in district courts has increased from 102 in 1970 to 629 in 1998 (from 0.09 to 0.25 per 100 physicians). The proportion of awards greater than 89 dollars 300 increased from 13.6% in 1976 to 65.4% in 1987. Among JMA members, claims increased 31% from 1987 to 1999, but the frequency of claims has remained at approximately 0.3 per 100 JMA members. The JMA's professional liability program offers a nonbinding out-of-court review of claims that is faster and less expensive than judicial resolution (a few months with no attorney required vs 35 months and attorney fees), but is a poor means of deterrence or discipline. Since JMA data represent only 43.5% of Japanese physicians, generalizations cannot be made about all Japanese physicians and institutions. The lack of data on all claims hinders adequate evaluation of dispute resolution methods, development of appropriate risk management activities, and proactive education for Japanese physicians.