Abdominal actinomycosis is a severe and progressive peritoneal infection, due to an anerobic gram-positive bacterium, Actinomyces israelii. The presence of a long-standing intrauterine device (IUD) is a well-known risk factor in young women. We report two cases of pelviperitoneal actinomycosis appearing in two young women with acute low abdominal pain. Abdominal CT demonstrated multiple solid or encapsulated peritoneal masses with marked contrast enhancement and infiltration of the adjacent mesenteric fat. Laparoscopy confirmed the presence of intraperitoneal abscesses which contained Actinomyces israelii. High doses of amoxicillin and clavulanic acid (Augmentine) were given and following CT scan after 2 and 6 weeks showed a slow, but complete, resolution of the lesions. Although the radiologic presentation of actinomycosis is nonspecific, the diagnosis should be raised in the presence of pseudotumoral mesenteric infiltration, particularly in young women with an IUD. Abdominal CT is a useful method for diagnosis and for follow-up.