We report three cases of pulmonary veno-occlusive disease which developed following treatment for malignant neoplasms. Two patients received single agent BCNU chemotherapy for malignant gliomas. The third patient underwent combination radiation and chemotherapy for Hodgkin's disease. Isolated case reports of pulmonary veno-occlusive disease following therapy for malignant disease are reviewed and clinical features summarized. Pulmonary veno-occlusive disease in this setting is thought to be rare. However, the diagnosis is rarely suspected clinically and is difficult to diagnose pathologically. Therefore, the true incidence of this complication is unknown and may be higher than believed. It is important that both clinician and pathologist be aware of this entity; otherwise, elastic tissue stains may not be performed and the diagnosis missed.