We diagnosed a 41-year-old female patient to be suffering from Chlamydia pneumoniae (C. pneumoniae) by using PCR and culture methods. She had a prolonged dry cough and slight fever. Her chest roentgenogram showed a segmental infiltration in the middle of the right lung field. We treated her with 400 mg of cefpodoxime proxetil (CPDX-PR) per day. On the 4th day after beginning the treatment with CPDX-PR, she still complained of a productive cough. We changed the treatment by using 300 mg of roxithromycin per day and these symptoms disappeared. To diagnose C. pneumoniae early, PCR, MIF and culture methods are very useful diagnostic tools.