Cervico-facial actinomycosis still occurs occasionally and should be included in the differential diagnosis of infectious processes in the jaws and the oral cavity. The typical actinomycosis-cases are clinically chronic in nature; however actinomycosis may be atypical with subacute or acute clinical manifestations. Among 37 cases of infectious processes in the jaws treated with extraoral incision between 1980 and 1985 in the Department of Oral Surgery, School of Dental Medicine, University of Berne, 3 (8%) were diagnosed as acute actinomycosis according to the following procedure. Prior to incision, pus was aspired under aseptic conditions. Presence of gram-positive branched filaments in the microscopically examined pus led to the suspicion of actinomycosis. This diagnosis was confirmed by cultivation of Actinomyces israelii using the anaerobic culture method, biochemical characteristics and gas-liquid chromatographic analysis of metabolic products. These 3 actinomycosis-cases were successfully treated by surgical removal of the suspicious foci and by administration of clindamycin per os for 16 days.