In 139 patients with facial paralysis, sudden hearing loss, vertigo, and lymphadenitis of the head and neck, the prevalence of borrelia burgdorferi serum antibodies was examined with the help of immunofluorescence assays for IgG- and IgM-antibodies, immunofluorescence assays after absorption of cross-reacting antibodies with treponema phagedenis, ELISA, and Western Blot. Six out of 22 patients with facial paralysis, 11 out of 72 with hearing loss, eight out of 45 with vertigo, and five out of 25 with lymphadenitis of the head and neck were seropositive. These patients were compared with a control group of 52 patients without any clinical signs of Lyme disease. The control group consisted of patients admitted for surgery of septal deformities (n = 19), squamous cell carcinomas (n = 27), and pleomorphic adenomas of the salivary glands (n = 6). In nine out of 52 patients in the control group, antibodies against Borrelia burgdorferi were detectable. According to Fisher's exact test, there was no statistical difference between the two groups as regards the prevalence of seropositive patients. Lyme disease is a doubtful major etiologic factor in facial paralysis, sudden hearing loss, or vertigo.