Physicians, dentists and patients were questioned as to their knowledge of endocarditis prophylaxis. about three quarters of the physicians and about half of the dentists were able to judge the risk of endocarditis correctly. Removal of calculus was underestimated as a risk for bacteriemia by physicians and patients alike. dentists overestimated the risk for endocarditis in the group of "non-risk-patients" (bypass), a fact resulting in an overdose/overuse of antibiotics. patients with lower education had less knowledge about the relation between their own personal risk and the necessary dental treatment.