Psittacosis infection is usually reported in adults aged around 30 to 60 years. We report here two cases of psittacosis in an elderly couple (76 and 77 years old) who jointly ran a pet shop. Psittacosis was diagnosed from a history of exposure to birds and from serological testing for Chlamydophilia avium. CASE REPORTSCase 1. Case 1 was that of a 76-year-old Japanese man who owned a pet shop selling parrots, parakeets, and budgerigars. He was admitted to our hospital due to general malaise and fever without cough or sputum, with no past history of such symptoms. Physical examination revealed the following: height, 160 cm; weight, 45.5 kg; arterial blood pressure, 170/92 mmHg; heart rate, 90 beats/min; body temperature, 38.3°C. Coarse crepitations were not detected, and lymphadenopathy was not present. Laboratory findings showed a white blood cell count of 10.05 ϫ 10 9 /liter (neutrophils, 90.8%; lymphocytes, 5.4%). Culture examination of sputum induced by 3% saline was negative. Blood culture examinations were likewise negative. Table 1 shows antibody titers against Mycoplasma pneumoniae, Chlamydophilia avium, and Chlamydophilia pneumoniae. Blood samples were submitted for examination of serum antibody titers to two Japanese commercial laboratories, SRL (Tokyo, Japan) and BML (Tokyo, Japan), and each serum antibody titer was measured. Complement fixation (CF) antibody titers against C. avium and M. pneumoniae were measured using a CF kit (Denka Seiken Co., Tokyo, Japan) according to the manufacturer's instructions at SRL. Microimmunofluorescence (MIF) testing against C. avium and C. pneumoniae was performed by BML according to the manufacturer's instructions (9). Enzyme-linked immunosorbent assay (ELISA) against C. pneumoniae was performed at SRL using a commercial kit (Hitachi Chemical Co., Tokyo, Japan) according to the manufacturer's instructions. CF antibodies against C. avium were not found in serum from blood samples taken on admission but were present at a dilution of 1/16 in serum taken 14 days later. The serum titer detected by MIF rose more than 32-fold from Ͻ8 in 14 days. The C. pneumoniae antibody titer using ELISA rose from 0.31 to 1.18, but the titer according to MIF was not considered elevated at 64-fold. A chest X-ray revealed infiltration shadows in the left upper and right lower lung fields. Computed tomography showed air space consolidation and ground-glass attenuation in the left upper and right lower lungs (Fig. 1A). Liver dysfunction was identified as follows: glutamic oxalacetic transaminase, 243 IU/liter (normal, 0 to 42 IU/liter), glutamic pyruvic transaminase, 56 IU/liter (normal, 0 to 37 IU/liter); lactate dehydrogenase, 602 IU/liter (normal, 106 to 211 IU/liter). The patient did not consent to bronchofiberscopic examination. He was treated with intravenous minocycline and sulbactam-ampicillin until serological and bacteriological reports became available. His body temperature normalized within 72 h. On day 9, treatment was switched from intravenous to oral minocycline and sulbactam-am...