Exposure to blood-borne viruses (BBVs) is considered a serious occupational risk for all health care workers (HCWs); however, those who perform exposure prone procedures (EPPs) are theoretically at increased risk. In the UK, the majority of dental procedures are classified as exposure prone. Whilst a vaccine exists to protect staff against hepatitis B virus (HBV), no vaccine is available against hepatitis C virus (HCV) or hepatitis G virus (GBV-C). Previous studies of HCV infection among dental staff have been retrospective and have not examined the role of non- occupational risk factors. They have also concentrated on risk to dental surgeons, rather than considering fully other groups such as dental hygienists and dental surgery assistants (DSAs). No studies have examined GBV-C infection in dental staff. The aim of this study was to determine the prevalence and determinants of hepatitis C virus (HCV) and GBV-C virus infection among dental surgeons, dental hygienists and DSAs working in general dental practice and the community dental service in the West of Scotland. This investigation was the first large-scale prospective study in Europe, of HCV and GBV-C infection among primary dental health care workers. The study was undertaken in the West of Scotland, an area of the UK recognised as having an extremely high prevalence of HCV among its injecting drug using population. The study was based on anonymous serological testing for HCV and GBV-C infection. The research nurse recruited from dental staff through their practice or community clinic. Demographic and risk factor information (personal and occupational) was collected via a standardised questionnaire administered by the research nurse during a confidential face-to-face interview. Whole blood was collected into plain bottles by venepuncture. Antibodies to HCV were detected by ELISA-3 (Ortho Diagnostics) using a pooling technique. All positive specimens were confirmed by RIBA-3 testing (Ortho Diagnostics). Antibody to GBV-C was detected using anti-HGenv ELISA (Roche Diagnostics GmbH) and an in-house PCR was used for GBV-C RNA. Dental staff (880) from 226 practices in Greater Glasgow (GGBH), Lanarkshire (LHB) and Ayrshire and Arran (AAHB), (61% of the total number of practices) participated. Dental surgery assistants made up the largest subgroup (53.3%), followed by General Dental Practitioners (35.9%)The overall prevalence of HCV antibodies was 0.1% (1/880, 95% CI 0% to 0.6%). The estimated maximum probability of occupationally acquired HCV infection per 100 person years was 0.02 for dentists; this would equate to a risk of 0.7% over a professional career of 35 years. The overall prevalence of GBV-C antibodies was 11.1% (98/880) and 4.6% were positive for GBV-C RNA (41/879), resulting in a cumulative prevalence of 15.7%.The DHCWs studied have an estimated prevalence of anti-HCV that is no greater than that in the local population, despite performing EPPs in an area with a high prevalence of anti-HCV. This suggests that HCV infection is not a significant occupational hazard for dental personnel. The prevalence of previous and current GBV-C infection among dental personnel was much higher than for HCV, but within the range reported for blood donor populations. There was some evidence that GBV-C may be a sexually transmitted infection. However, transmission through intimate contact with saliva is also suggested. Recently, dental treatment has been suggested as a potential source of HCV infection for a number of infected individuals for whom the route of infection is unknown. Our results imply that dental personnel do not represent a large reservoir of infection to patients. Further research should focus on person-to-person transmission within the dental surgery as a possible source of infection.