Since recent studies suggested a role for Parachlamydia in atherosclerosis, we investigated 354 patients with or without atherosclerosis for Parachlamydia infection. Six patients exhibited anti-Parachlamydia IgG. No patient presented IgM. Parachlamydial DNA was not amplified from peripheral blood mononuclear cells. There was no association between atherosclerosis and Parachlamydia infection.