Pulmonary hemorrhage is a rare cause of death in patients with acute leukemia. Within a 2-month period the authors observed two fatal pediatric cases, which were associated with opportunistic organisms of the genus Micrococcus. Both patients were receiving consolidation treatment for acute lymphoblastic leukemia. The authors discuss the causes of pulmonary hemorrhage in patients with leukemia and review the relevant literature. Micrococci have previously been considered as non-pathogenic, but there is considerable evidence for morbidity and mortality occurring, particularly in immunocompromised patients. The authors propose that micrococcal infection may have been a major predisposing factor for pulmonary hemorrhage in these thrombocytopenic patients.