Dentists were surveyed regarding a history of hepatitis and the presence in the blood of hepatitis B surface antigen (HBsAg) and antibody (anti-HBs) to determine whether they were at high risk of exposure to hepatitis B virus. Of 288 Canadian dentists 5.2% gave a history of hepatitis after graduation. This proportion is similar to that for 1462 Ontario dentists (6.3%) and that for 3162 accountants (5.1%) who had previously completed a mailed questionnaire. One dentist (0.3%) was HBsAg-positive and 42 (14.6%) were anti-HBs-positive. Of 210 healthy volunteer blood donors matched for age, sex and ethnic origin with the group of dentists none was HBsAg-positive and 2.9% significantly fewer (P less than 0.005), were anti-HBs-positive. Among Ontario blood donors 0.3% were HBsAg-positive and 3% were anti-HBs-positive. Thus, in Canada, dentists are not at increased risk of acquiring clinical hepatitis or becoming carriers, but they are more likely than other groups to have anti-HBs in the blood. Among dentists from outside Canada a higher proportion had a history of hepatitis (10.3%) and were HBsAg-positive (1.6%), but approximately the same proportion were anti-HBs-positive (15.9%).