One hundred and fifty patients with Bell’s palsy were examined for evidence of a preceding viral infection. Twenty-one patients reported having had such an infection, in most cases during the week preceding the onset of neurological symptoms. Fourteen patients had fever. In 12, there was an enlargement of the submandibular lymph nodes. Nineteen patients had leucocytosis and another 6 a relative lymphocytosis. The ESR was temporarily elevated in 11 patients. Complement fixation tests for influenza A and B, parainfluenza 1 and 2, adenovirus, mumps, West-Nile fever and herpes simplex were negative in all the patients tested. Attempts to cultivate a virus from throat swabs, feces and blood also failed.