This study was designed to determine the role of dental flossing in producing transient bacteremias. An improved protocol that provides for repeated samplings of blood was developed. Four patients had 32 blood cultures taken (16 before flossing and 16 after). Two of the patients had no periodontal disease and two had only marginal gingivitis. The results showed that the patients who flossed daily developed no bacteremias but that patients who delayed flossing from 1 to 4 days developed bacteremias 86% of the time. It is important that patients who have a history of rheumatic fever and those who have internal prosthetic devices be cautioned regarding sporadic flossing. While gingival bleeding was not significantly related to bacteremias in this study, further investigation is needed to ascertain how flossing in various types of periodontal disease relates to bacteremias.