Actinomycosis is an anaerobic infection caused by actinomycetes, which are part of the normal flora in the oral cavity and intestine. Antecedent disease or surgery predisposes to infection, and involved tissue becomes indurated and forms multiple draining fistulae discharging characteristic sulfur granules. Three principal clinical syndromes are described: cervicofacial, thoracic, and abdominal. Recently pelvic actinomycosis has become more prevalent and associated with women who use the intrauterine device. The diagnosis of actinomycosis usually is made at surgery. Biopsied material histologically demonstrates sulfur granules and filamentous gram-positive rods. The differential diagnosis includes cancer and other chronic infections. Treatment consists of appropriate antimicrobial therapy and often surgery including incision and drainage or excision of abscesses, drainage of empyemas, and removal of persistent sinuses.