Nine cases of thoracic actinomycosis treated in the period from 1976 to 1990 were reviewed. Among them, 4 cases were children. The clinical symptoms and laboratory examinations were non-specific. Chest roentgenographic manifestations including nodular (3 cases), infiltrations (4 cases), and infiltrations with pleural changes (2 cases) were also non-specific. Chest wall masses were noted in four patients. There were no cases correctly diagnosed on admission. The diagnosis of thoracic actinomycosis was made from thoracotomy in 6 cases, from culture of chest wall mass incisional specimens in 2 cases and from bronchoscopic biopsy in 1. All the patients received antibiotics, however the varied duration of postoperative antibiotics did not change the outcome. No mortality or recurrence was noted in our 9 patients with a mean follow-up of 1.9 years (from 2 months to 6 years.) We conclude that surgical intervention is still the cardinal method for diagnosis and treatment. Establishment of the role of postoperative antibiotics will need further prospective study. The prognosis of thoracic actinomycosis is fairly good.