A 56-year-old man with fever, headache, cough and sputum was admitted to another clinic. Chest X-ray examination revealed infiltrates in the upper lobe of the right lung. Cefem and aminoglycoside therapy was not effective, and the infiltrates migrated from the right upper lobe to the right middle and lower lobes and then to the left lung. He was transferred to our clinic, and laboratory data showed that CRP was 6+; ESR, 119 mm/1 h; WBC, 3000/mm3; and CAR, 512. The tentative diagnosis of atypical pneumonia was based on the positive agglutination test for Legionella pneumophila, and treatment with erythromycin, minocycline and rifampicin resulted in alleviation of symptoms and resolution of the infiltrates in the lungs. Complement fixation titer for Chlamydia was 128 at admission and was elevated to 512 after 2 weeks. Indirect fluorescent antibody for Legionella was negative. Transient liver dysfunction was also observed.