Legionella bozemanii, a rare cause of pneumonia, has a predilection for patients with impaired cellular immunity and underlying disease. We report the 12th culture-proven case of this infection, acquired in the community by a patient undergoing chemotherapy for chronic lymphocytic leukemia. The diagnosis was established when studies of bronchoalveolar lavage fluid produced a positive reaction with species-specific fluorescent antibody and growth on selective culture media. Although erythromycin was administered within 48 hours after the initial examination, the clinical condition did not improve substantially until rifampin was added to the antimicrobial regimen.