A case of pulmonary actinomycosis of periodontal origin is presented. Microbiologic testing including culture and typing of multiple systemic and oral lesions revealed the presence of Actinomyces naeslundii and A viscosus in all sites. In addition, biopsies demonstrating branching filamentous forms and "sulfur granules" were found in exudates from the lungs, submandibular region and left quadrants of the oral cavity. Seeding of tooth-associated materials containing Actinomyces sp into the pulmonary field may have resulted in this case of pulmonary actinomycosis. Therapy of the pulmonary and periodontal infections was completed and the patient is maintaining satisfactory health 18 months later.