The pathologic features in pulmonary specimens are reported from 32 open thoracotomies of 20 patients with chronic granulomatous disease (CGD). The pattern of inflammation present in the resected material varied, but a granulomatous component was present in each case. In 78% of the specimens, a distinctive form of granuloma was found: a neutrophilic microabscess surrounded by palisading histiocytes. In four specimens eosinophils were also found within the microabscesses. This feature was found exclusively in cases of fungal infection. Fungal organisms were found by culture in 18 specimens (56%) and in 17 of these specimens (94%), they also were seen by histopathology. In 9 cases (28%) routine bacterial cultures were positive, and in one case an atypical Mycobacterium was cultured. These organisms were not prospectively identified on special stains of histologic sections in any of the cases. Abscess formation was found more commonly in pure fungal infections (41%) than in pure bacterial infections (14%). In contrast to earlier reports, well-formed granulomas with giant cells were not specific for fungal infections. In this series, they were present in 57% of cases with pure bacterial infections. A subset of the patients received gamma interferon therapy or granulocyte transfusions before the surgical procedures. No differences in the histopathology of the inflammation were associated with granulocyte transfusions, but gamma interferon therapy was associated with a reduction in necrotizing granulomatous inflammation. Additionally, one case of severe cytomegalovirus pneumonitis is described in a CGD patient receiving chronic steroid therapy.