-Objective: To investigate the possible relationship between atherothrombotic stroke and Chlamydia pneumoniae. Method: 150 patients with carotid atherothrombosis were enrolled. The casuistic was divided in three groups: ischemic stroke (IS): 65 patients; transient ischemic attack (TIA): 26 patients; and control: 59. The IS or TIA onset was up to 30 days from the beginning of the study. Carotid atheromatoses was diagnosed by Doppler-ultrasonography. Patients with cardioembolic risk or non-atherothrombotic origin were excluded. Comparisons were done between the three groups, and within each group according to the different age subgroups, to the main arteries affected, and to the atherogenic risk factors. Bacteria detection was done using polimerase chain reaction. Results: Only one patient tested positive for C. pneumoniae belonging to the control group. Conclusion: These results do not suggest that C. pneumoniae participated in the onset of IS or TIA or that it has a role in carotid plaque destabilization.Key WOrDS: stroke, chlamydia, atherosclerosis, risk factors, cerebral infarct.Chlamydia pneumoniae e acidente vascular cerebral aterotrombótico: existe relação direta?Resumo -Objetivo: Investigar a possível relação entre Chlamydia pneumoniae e acidente vascular cerebral aterotrombótico (AVC). Método: 150 pacientes com aterotrombose carotídea foram estudados. A casuística foi dividida em 3 grupos: AVC: 65 pacientes; ataque isquêmico transitório (AIT): 26 pacientes e controles: 59. O início do AVC ou AIT era até 30 dias da inclusão no estudo. A ateromatose carotídea foi diagnosticada por ultrassonografia com Doppler. Os pacientes com risco cárdio-embólico ou sem evidência de aterotrombose foram excluídos. Foram estabelecidas comparações entre os 3 grupos e dentro de cada grupo, formado subgrupos de acordo com diferentes idades, território arterial comprometido e fatores de risco. A detecção da bactéria foi feita por reação de polimerização em cadeia. Resultados: Somente um paciente, pertencente ao grupo controle, teve resultado positivo. Conclusão: estes achados não sugerem que a C. pneumoniae participe no desencadeamento do AVC ou AIT ou que tenha papel na desestabilização da placa. PAlAVrAS-ChAVe: acidente cerebral vascular, aterosclerose, fatores de risco, infarto cerebral, chlamydia. Several studies have reported infections as a risk factor for stroke (AVC) 1,2 which could act in the unleashing, the progression or the destabilization of the atherosclerotic plaque 1 . The confirmation of such hypothesis would open an important space, both for an eventual specific therapeutic approach in the acute phase of the stroke and for its prevention. There is an increasing volume of evidences suggesting the association between inflammation, infection, and atherosclerosis 3,4 , although that relation is still not well established 5 . There are authors that defend that the inflammation is the key for the development and the progression of atherothrombosis 3,6 . The most frequent infectious agent implicated to ather...