The number of dental patients who have medical illnesses is increasing at the hospital of the Faculty of Dentistry, Tokyo Medical and Dental University. Although prosthodontic treatments are considered less invasive in all dental treatments, invasive procedures such as tooth extraction may be required occasionally. Therefore, it is necessary to treat patients in consideration of their condition. Under this situation, a clinical survey was conducted by health questionnaires answered by the patients who visited our clinic between October 1992 and March 1997. The number of patients whose illness was heart disease, hypertension, diabetes, nephritic disease, hepatitis, tuberculosis, hemodyscrasia, asthma, epilepsy, and so on during dental treatment was higher than the national average according to the Ministry of Health and Welfare. Dental psychosomatic diseases such as TMD and dental phobia were increased every year. These data reflect the contemporary disease structure in Japan characterized by the spreading of life-style related diseases and increase of neuropsychological and infectious diseases.