A case of actinomycosis mimicking abdominal neoplasm in a 56-year old woman is presented. Actinomyces israelii is a common saprophyte found in the mouth and gastrointestinal tract. It is an anaerobic, Gram-positive, branching filamentous fungus related in many respects to the bacteria. Damage to the mucosa by trauma, disease or surgery is an essential prerequisite to infection with this organism. In 20% of the cases the abdomen is involved, but an abdominal mass is a rare presentation. In such cases diagnosis prior to exploratory laparotomy is difficult.