Sera were collected from 50 practising dental surgeons and 50 control subjects matched for age (+/- 1 year) and sex. Each participant completed a questionnaire including personal details and, in the case of dentists, information relating to protective work-wear and other cross-infection control measures employed within the surgery. The sera were examined by complement fixation tests for antibodies to influenza A, influenza B, respiratory syncytial virus and adenovirus. The dental group had a significantly elevated prevalence of antibodies to influenza A (P = 0.01), influenza B (P < 0.001) and respiratory syncytial virus (P = 0.001) compared with the controls. More dentists than controls also carried antibodies to adenoviruses, although this difference did not attain statistical significance. Wearing of masks or eye protection did not markedly reduce infection with these viruses among the dentists. It is concluded that dentists are at occupational risk of infection with respiratory tract viruses, and that mask- or spectacle-wearing afford little protection.