Nonlymphomatous lymphoid disorders of the lung consist of several entities with varied histology and clinical behavior. On the basis of histologic appearance, six lesions can be identified. They include Castleman's disease, plasma-cell granuloma, pseudolymphoma, lymphocytic interstitial pneumonitis, angioimmunoblastic lymphadenopathy, and lymphomatoid granulomatosis. These conditions in 22 patients, their radiologic and histopathologic features, and their relationship to the malignant lymphomas are discussed. Although a radiographic diagnosis may be suggested, overlapping features mandate open-lung biopsy in most instances. The frequent evolution toward malignant lymphoma with lymphomatoid granulomatosis and pseudolymphoma necessitates close follow-up and sometimes aggressive therapy.