Abstract Seroepidemiological and histopathological studies have suggested a link of atherosclerosis with chronic Chlamydia pneumoniae infection. The present study was designed to examine the effect of C. pneumoniae on expression of basic fibroblast growth factor (bFGF) and platelet-derived growth factor (PDGF) in human endothelial cells. Using reverse transcription-polymerase chain reaction, immunoblotting and enzyme-linked immunosorbent assay we found stimulation of bFGF expression depending on the number of infecting bacteria and the time of infection as well. This stimulatory effect was diminished by heat and UV light treatment of the chlamydial inoculum, suggesting that viable bacteria but not bacterial LPS may be essential for eliciting this growth factor. In contrast, the expression of both PDGF-A and PDGF-B was not increased following C. pneumoniae infection. This study demonstrates that C. pneumoniae activates endothelial cells to produce bFGF, a growth factor which is linked to the development of atherosclerotic plaques.