We reviewed records of patients with hematologic malignancy requiring mechanical ventilation (MV) from 1976 to 1985 (excluding postoperative MV less than 48 hours). There were 119 episodes in 116 patients. In-hospital mortality was 82 percent. Of 21 (18 percent) episodes survived, median duration of survival was 12 months. Survivors did not differ from nonsurvivors in age, leukocyte count, or duration of MV. Survival for chronic lymphocytic leukemia was 42 percent, for other leukemias 16 percent, Hodgkin's disease 29 percent, and non-Hodgkin's lymphomas, 6 percent. Bronchoscopy was performed in 28 patients, resulting in a diagnosis of infection, hemorrhage, or malignancy in 19 cases. Open lung biopsy (OLB) was obtained in 23 patients, yielding a diagnosis of interstitial inflammation or fibrosis (13 cases), drug effect (three), malignancy (two), hemorrhage (one), Pneumocystis (seven), aspergillosis (two), and Legionella (one). Only two patients survived following OLB. Despite intensive management and adequate diagnosis, respiratory failure in patients with hematologic malignancy carries a high mortality. Although these data may help identify groups with a limited prognosis for long-term recovery, patient care must be individualized.