Epidemiology of diseases of unknown etiology, specified as "intractable diseases".

In Japan, epidemiological studies on intractable diseases have been undertaken and greatly promoted for more than 20 years by the Research Committee on Epidemiology of Intractable Diseases, with the financial supports from the Ministry of Health and Welfare of Japan. In this paper, chronological history of development of the Research Committee and some scientific accomplishments by the recent Research Committee (1993-1995) were summarized, mainly focusing on descriptive, analytical and other epidemiological studies. Hoped is that the readers are to be acquainted with the recent research activities by the Research Committee and seek for possible international collaborations in epidemiological studies on intractable diseases.