Actinomycosis is an uncommon disease with clinical and radiographic findings that overlap those of other inflammatory and neoplastic conditions. A retrospective review of CT scans in six proved cases revealed a spectrum of findings, including soft-tissue mass with various degrees of infiltration and abscess formation. Administration of IV contrast material was helpful in defining the loculations of the abscess in two cases. Areas of involvement included the neck (two cases), liver (one case), abdominal wall (one case), thorax (one case) and kidney and retroperitoneum (one case). CT findings of a soft-tissue mass in the neck, lungs, or abdomen, with or without a draining sinus or fistula, raise the possibility of actinomycosis in patients with clinical findings that suggest a subacute or chronic inflammatory process.