Dentists have a particular risk of acquiring viral hepatitis because of their close contact with blood and saliva during dental manipulations--especially as the majority of dentists do not use gloves during work and often have small cuts and abrasions on their hands. On the other hand personnel in the dentist's office offers several potential modes of parenteral and oral-intestinal transmission of hepatitis. In order to find out the risk of dentists exposing themselves to hepatitis-infection (especially hepatitis B-infection) we performed a questionnaire-study among practicing dentists all over Oberbayern. 858 replies were received after distribution of 1030 questionnaires (participation: 83.3%) and could by analyzed. 116 dentists had had a hepatitis during their professional work (13.5%). The frequency of hepatitis among the younger colleagues--who were practicing from 1 to 14 years--was about 5%. The number of hepatitis-infections increased continually up to 33% after 35--39 years of professional activity. In a second study blood samples were taken from 773 dentists and were tested for HB3Ag by radioimmunoassay. Of these 773 blood samples taken 25 (3.5%) were found to be antigen-positive. Compared to the general population the risk of infection is 6- to 30 times higher in dentists. The challenge of hepatitis-virus-infection can at present be met only-and at least in part-by scrupulous attention to prophylactic measures, such as using disposable gloves, needles and syringes and in autoclaving all non-disposable equipment. Besides dental personnel and patients should be screened at regular intervals for the presence of HBsAG.