A retrospective study of patients hospitalized for infections associated with partially erupted third molars during a 10-year period (1985-94) showed a total of 17 cases: 6 women and 11 men, aged 18 to 57 years. Eight patients were in the third decade. No deviation from me habits of the general population with regard to cigarette smoking and alcohol consumption or overrepresentation of general health problems was found. All infections were of pericoronal origin. Bacteriologic cultures from six patients showed mixed aerobic—anaerobic oral flora, without any penicillin-resistant strains. The incidence rate of serious orofacial infections associated with partially erupted third molars was calculated to be 0.016 cases per year per 1000 patients at risk.