A 42-year-old man with an atypical pneumonia. He had chest pain and a dry cough for 3 weeks, was dull at the left base clinically, and had left lower zone consolidation on chest radiography. The pneumonia spread despite oral ampicillin and cloxacillin. Blood culture grew Listeria monocytogenes and white cell count showed a monocytosis. He responded to intravenous penicillin and gentamicin with complete X-ray clearance.