Actinomycotic infection is uncommon and primary actinomycosis of the lung and chest wall has been less frequently reported. This disease may present as chronic debilitating illness with radiographic manifestation simulating lung tumor, pulmonary infiltrating lesion, or chronic suppuration. From 1984 to 1990, we experienced 17 cases of thoracic actinomycosis. There were nine patients who presented with a clinical picture of a suppurative lesions and the remaining eight were suspected of having primary lung tumor initially. In no case was an accurate diagnosis made at the time of hospital admission. Final diagnosis was based on aspiration (n = 3), anaerobic sputum culture (n = 1), bronchoscopic biopsy specimens (n = 4), and histologic examination of the resected tissue in the remaining 9 patients who received surgical excision. Among the 17 patients, 8 were treated medically and the other 9 received surgical intervention followed by antibiotic treatment. Regarding the surgically treated patients, suspected malignancy is the most common indication for operation (seven of nine). However, both medically and surgically treated patients achieved good clinical results, and the postoperative courses were uneventful. We would like to remind physicians of this unusual entity and review our own experience with particular emphasis on the clinical diagnosis and management of this unique disease.