Introduction: Bronchoalveolar lavage (BAL) is often performed in leukemia and lymphoma patients with pulmonary infiltrates, mainly to rule out infection. However, malignant hematopoietic infiltrates are uncommon and a comprehensive cytologic study has not yet been performed. Materials and methods: We retrospectively reviewed all BAL samples from our institution for the past 22 years (November 1992-October 2014). Results: There were 37 cases of hematologic malignancies identified on BAL specimens (21 female patients and 16 male patients, age 22-80 years). Eighteen patients (49%) had pneumonia-like symptoms at the time of initial diagnosis of their malignancy, including fever, dyspnea, respiratory distress/hypoxia, and cough. The biopsy-proven cases were 25 leukemia (12 acute myeloid leukemia, 6 acute promyelocytic leukemia, 2 acute monocytic leukemia, 2 acute myelomonocytic leukemia, 1 chronic myeloid leukemia in blast phase, 1 large granular leukemia, and 1 plasma cell leukemia), 11 lymphoma (8 diffuse large B-cell lymphoma, 1 mantle cell lymphoma, 1 natural killer/T-cell lymphoma, and 1 T-cell lymphoma), and 1 multiple myeloma. Chest X-ray findings included opacities, consolidation, and interstitial edema. Four patients had BAL specimens with concomitant microorganisms. Eighteen patients subsequently died (2 days to 4 years), 15 were alive (3 weeks to 8 years of follow-up), and 4 were lost to follow-up. Conclusions: BAL is especially important in distinguishing inflammatory/infectious processes from neoplastic disorders because many patients with hematologic malignancies can have pneumonia-like symptoms as part of their initial disease presentation. Causative pathogens are identified in only a minority of malignant BAL specimens from these patients. Lung involvement in patients with hematologic malignancies carries a poor prognosis.