Bacterial endocarditis (BE), a rare heart infection caused by a bacteremia, has frequently been blamed on but rarely caused by dental procedures. Viridans group streptococci are found abundantly in the mouth and the gingival sulcus but have been surpassed by staphylococci as the leading cause of BE. Antibiotic prophylaxis has been recommended before dental procedures in patients at risk for BE, but it remains controversial because studies have failed to show that antibiotic prophylaxis is an effective preventive for BE or that dental procedures are an important cause of BE. The risks and costs of antibiotic prophylaxis, including antibiotic resistance, cross-reactions with other drugs, allergy, anaphylaxis, and even death, may exceed the benefits in preventing BE. The rationale for the use of antibiotic prophylaxis to prevent BE allegedly caused by dental procedure bacteremias must be seriously reexamined based on recent evidence, particularly the absolute risk rates for endocarditis after a given dental procedure.