The cause of Bell's palsy remains unknown even though available evidence suggests that infection could be a factor. In recent studies, Chlamydia pneumoniae has been associated with neurologic diseases such as multiple sclerosis. In the present study, the association of C pneumoniae with Bell's palsy was studied with the use of serology and polymerase chain reaction to test tear fluid and peripheral blood mononuclear cells from 21 patients with Bell's palsy and 21 control subjects. C pneumoniae DNA was detected from tear fluid samples in 1 patient with Bell's palsy and in 2 healthy control subjects. Whether this indicates earlier disease or subclinical infection remains to be studied. However, an association between Bell's palsy and acute C pneumoniae infection could not be shown.