Background and Objective. Serological evidence of infection with Chlamydia pneumoniae has been associated with cardiovascular diseases, but the relationship with stroke and its risk factors remains not completely understood. The aim of this study was to determine whether serological evidence of infection with Chlamydia pneumoniae was associated with the risk of ischemic stroke and any of investigated stroke subtypes. Material and Methods. Confirmed stroke cases (n=102) were compared with gender- and agematched control patients (n=48). The patients with stroke were divided into 3 groups according to the TOAST criteria: atherothrombotic (n=36), cardioembolic (n=47), and of undetermined etiology (n=19). Plasma levels of IgG antibodies to Chlamydia pneumoniae were measured by enzymelinked immunosorbent assay. Results. There was a significant association between seropositivity to Chlamydia pneumoniae and stroke. Anti-Chlamydia pneumoniae IgG antibodies were detected in 64 case patients (62.7%) and 17 control patients (35.4%) (χ2=9.8; df=1; P=0.002). IgG seropositivity to Chlamydia pneumoniae was linked to all the analyzed etiological subtypes of stroke. Conclusion. This study showed that IgG seropositivity to Chlamydia pneumoniae was associated with stroke and all the analyzed etiological subtypes of stroke.