Of 91 adult patients with respiratory tract infections, 13 (14%) had serological evidence of recent infection with Chlamydia pneumoniae. The clinical picture was consistent with asthmatic bronchitis in three patients, whilst exacerbations of chronic obstructive pulmonary disease were present in five subjects and, pneumonia was diagnosed in the remaining five. Our findings provide evidence of an aetiological association between C. pneumoniae and respiratory infections in our region (Bari, South Italy).