Aim: To determine whether the common respiratory pathogen, Chlamydia pneumoniae, was associated with atherosclerotic plaques in Australian subjects. Methods: A total of 29 coronary atherosclerotic lesions and 18 normal coronary arterial samples were tested for the presence of C. pneumoniae by PCR and immunofluorescence methods. Results: Chlamydia pneumoniae was detected in 15 of the atheromatous lesions as well as in three of the normal tissues; the immunofluorescence assay was more sensitive (P = 0.028) than PCR (P = 0.26). Conclusions: These findings contradict previous Australian studies which did not detect C. pneumoniae in atherosclerotic plaques, thereby discounting the speculation that its absence was likely due to geographical variation. The detection of the bacterium in some of the normal tissues suggests that C. pneumoniae infection might be an initial trigger of atherosclerotic development.