Traditional treatment of otosyphilis with penicillin and corticosteroids has achieved hearing improvement; however, selecting which patients with a positive fluorescent treponemal antibody absorption (FTA-ABS) test will benefit from treatment remains a problem. In order to study this problem, 18 patients with cochleovestibular dysfunction of unknown etiology and positive syphilis serology were treated with intravenous penicillin and corticosteroids. In addition, lumbar puncture and human immunodeficiency virus (HIV) testing were performed on all patients. Hearing improved in 5 (31%) of 16 patients, tinnitus decreased in 11 (85%) of 13, and vertigo improved in 6 (86%) of 7. Factors associated with hearing improvement were hearing loss present less than 5 years, fluctuating hearing, and age less than 60. Improvement was unrelated to the severity of the loss or previous therapy. All patients with cerebrospinal fluid abnormalities, including two patients with HIV disease, had subjective improvements. A diagnostic and treatment protocol is presented.