AIMS: The aims of this study were to (1) investigate the incidence of bacteraemia following flossing in subjects with chronic periodontitis or periodontal health; (2) identify the micro-organisms in detected bacteraemias; and (3) identify any patient or clinical factors associated with such bacteraemia. MATERIAL AND METHODS: Baseline blood samples were obtained from 30 individuals with chronic periodontitis (17 M:13 F, 29-75 years) and 30 with periodontal health (17 M:13 F, 28-71 years) following a non-invasive examination. Each subject's teeth were then flossed in a standardized manner and blood samples obtained 30 s and 10 min. after flossing cessation. Blood samples were cultured in a BACTEC system and positive samples subcultured for identification. RESULTS: Forty per cent of periodontitis subjects and 41% of periodontally healthy subjects tested positive for bacteraemia following flossing. Viridans streptococci, which are commonly implicated in infective endocarditis (IE), were isolated from 19% of positive subjects and accounted for 35% of microbial isolates. Twenty per cent of subjects had a detectable bacteraemia at 10 min. post-flossing. No patient or clinical factors were significantly associated with post-flossing bacteraemia. CONCLUSIONS: Dental flossing can produce bacteraemia in periodontally healthy and periodontally diseased individuals at a rate comparable with that caused by some dental treatments for which antibiotic prophylaxis is given to prevent IE.