We present a case of pulmonary actinomycosis of the right upper lobe, which was secondary to radiation pneumonitis. The patient underwent an uncomplicated left upper lobectomy en bloc with the 1st-2nd-3rd ribs and adjuvant radiotherapy, for a stage T3N0M0 (IIb) superior sulcus, adenocarcinoma, one-year ago. Radiation pneumonitis complicated his late postoperative course and he received steroids for 3 months. Four months later he suffered from thoracic pain, exhaustion and minor hemoptysis. Chest X-Ray showed two lesions, 0.5 and 1.5 cm of maximal diameter, located in the right upper obe. CT scan gave the evidence of metastatic disease and bronchoscopy was negative for intraluminal findings. The patient had exacerbation of hemoptysis and repeated Papanikolaou stained cytological examination of the sputum sample revealed “piles of actinomyces”. The patient received penicillin therapy for 6 months and he had improvement of the clinical condition and decrease by half of the diameter of right upper lobe lesions. Pneumon 2002, 15(1):31-35.