SUMMARY. Pulmonary actinomycosis is a rare, chronic granulomatous disease, which is difficult to diagnose because it is commonly confused with other granulomatous infections or lung cancer. The case is reported of a 48 year-old man, a smoker, who presented with a 30 day history of productive cough with blood tinged sputum and a peripheral lung mass on the chest X-ray. He underwent full clinical and laboratory evaluation including bronchoscopy, which was unrevealing. Because of the haemoptysis the patient refused a computerized tomography (CT) guided fine needle aspiration biopsy, and proceeded directly to surgery. Following a right posterolateral thoracotomy and lysis of adhesions, a wedge resection of the right lower lobe mass in the lung was performed and sent for frozen section which was negative for malignancy. His postoperative course was unremarkable. The final pathology report established the diagnosis of pulmonary actinomycosis. Pulmonary actinomycosis should be included in the differential diagnosis of a lung mass in a patient presenting with haemoptysis, because an early and accurate diagnosis will preclude unwarranted surgery. Pneumon 2009, 22(3):258-261.