Intrathoracic manifestations of histiocytic lymphoma were reviewed in a retrospective study of 112 nonselected patients who had at least a 2 year follow-up period or had died. In 50% (56 cases), intrathoracic histiocytic lymphoma was found. In 26% (29 cases), intrathoracic manifestations were initially seen. In 11% (12 cases), the disease was completely confined to the chest. Mediastinal involvement was present in 25% (28 cases), hilar involvement in 17% (19 cases), pulmonary involvement in 20% (22 cases) (interstitial or mixed interstitial alveolar infiltrates in 13% [14 cases], nodular lesions in 8% [nine cases], localized homogeneous consolidations 5% [six cases]), and pleural involvement in 18% (20 cases), of which 4% (four cases) had localized pleural plaques. Intrathoracic manifestations of histiocytic lymphoma are similar in the early and late stage of the disease. However, sarcoidlike hilar and mediastinal involvement (3% [three cases]) and a localized mass in the lower posterior mediastinum (4% [four cases]), the anterior mediastinum (2% [two cases]) or unilaterally in a hilum (2% [two cases]) were initial presentations not encountered late in the disease. Because of the rapid progression of this entity, early recognition of its intrathoracic manifestations is mandatory for effective therapy.