We have described two patients with abdominal actinomycosis, one with extensive intra-abdominal and thoracic disease mimicking metastatic carcinoma, and the other having the rarely described clinical entity of retroperitoneal disease without evidence of intra-abdominal involvement. Both patients responded well to appropriate therapy, but had unnecessary surgical procedures. The surgeon's role in cases of actinomycosis should be limited to the provision of a diagnosis when necessary.