Although open lung biopsy (OLB) is frequently employed for diagnosis of pulmonary lesions in patients with Hodgkin's disease, the actual efficacy of the procedure in establishing a diagnosis in these patients, and its effect on their treatment and clinical outcome, have not been evaluated. We reviewed the results of OLB in 41 patients with previously diagnosed Hodgkin's disease (17 with stage II disease, 10 with stage III, and 14 with stage IV) who had pulmonary opacification on chest roentgenogram. Nineteen (46%) diagnoses were specific and 22 nonspecific. The most common specific diagnosis was Hodgkin's disease (12 patients); the others were Pneumocystis carinii pneumonia (3), solitary fungal granuloma (2), cytomegalovirus pneumonia (1), and primary lung adenocarcinoma (1). Specific diagnoses were made in 11 (69%) of 16 patients with discrete nodules or masses but in only eight (32%) of the 25 patients with non-nodular radiographic opacification. Eleven (58%) of 19 patients who were asymptomatic or had had symptoms for longer than 4 wk had specific diagnoses, compared to one of six patients (17%) symptomatic for 1 wk or less. Survival of hospitalization correlated more with stage of Hodgkin's disease than with specific diagnosis. However, treatment was changed after biopsy in 22 (54%) of the patients. The results suggest that OLB can be helpful in the management of patients with Hodgkin's disease and pulmonary infiltrates, both in establishing a diagnosis and in assisting the patients' management. OLB appears to be more helpful in patients with Hodgkin's disease than in patients with acute nonlymphocytic leukemia or the acquired immunodeficiency syndrome and pulmonary infiltrates.