The main aim of this thesis was to evaluate the effect of prednisolone and valaciclovir in a large number of Bell's palsy patients. The incidence and intensity of pain around the ear, in the face or in the neck during the first two months of palsy, and its prognostic value, was also assessed. We also investigated how study design and choice of analysis method affect the rate of facial recovery. Furthermore, the agreement between the Sunnybrook, House-Brackmann and Yanagihara facial grading systems was evaluated. From May 2001 to September 2007, a prospective, randomised, double-blind, placebo-controlled, multicentre trial with 12-month follow-up was performed in patients with Bell's palsy. Of 839 randomised patients, 829 were included in the intention-to-treat analysis; 206 received placebo plus placebo, 210 prednisolone plus placebo, 207 valaciclovir plus placebo, and 206 prednisolone plus valaciclovir. Time to recovery was significantly shorter in the 416 patients who received prednisolone compared with the 413 who did not (p<0.0001). At 12 months, 300 of 416 patients (72%) in the prednisolone group had recovered compared with 237 of 413 patients (57%) in the no prednisolone group (p<0.0001). Valaciclovir was not found to affect time to facial recovery or outcome at 12 months. Prednisolone and/or valaciclovir did not affect the incidence or intensity of pain. Presence of pain at day 11 to 17 indicated a worse prognosis for facial recovery at 12 months. We also found that recovery rates in a Bell's palsy trial are substantially affected by the choice of analysis method and definition of facial recovery. We used weighted Kappa statistics in 100 examinations of patients with facial palsy to assess the agreement between the Sunnybrook, House-Brackmann and Yanagihara scales. The highest agreement was found between the regional Sunnybrook and Yanagihara scales. An evaluative difference between the Sunnybrook and House-Brackmann systems was observed.