THE PHYCOMYCETES (Mucor, Absidia, and Rhizopus) are common saprophytes. Infection with these fungi occurs primarily in patients with severe underlying illness, especially leukemia, lymphoma, and uncontrolled diabetes mellitus.1 Our case is note-worthy because Rhizopus pneumonia occurred without obvious predisposing factors. Report of a Case A 66-year-old man was hospitalized because of cavitary pneumonia. Two months previously, bilateral knee surgery was performed, with cephalothin sodium prophylaxis. Two weeks before admission, fever, chills, pleurisy, and cough with yellow, blood-tinged sputum developed. One week before admission, a chest x-ray film disclosed left lower lobe infiltrate, and penicillin V potassium was given orally. Despite clearing of the initial infiltrate, symptoms worsened, and the chest x-ray film showed a new, left upper lobe infiltrate with central cavitation (Figure). Results of a physical examination on admission were unremarkable except for bibasilar and left axillary rales, decreased knee mobility, and moderate dyspnea. Multichannel (SMA-12) chemistry profiles