In a prospective, controlled, and randomized study, we compared the outcome of 101 Bell's palsy patients treated with acyclovir (54 patients) or prednisone (47 patients). The acyclovir dosage was 2400 mg (800 mg three times a day) for 10 days, and prednisone was given as a single daily dose of 1 mg/kg of body weight for 10 days and tapered to 0 over the next 6 days. Minimum follow-up was 3 months in all patients. Patients in the prednisone group had better clinical recovery than those treated with acyclovir. Less degree of neural degeneration was observed in the prednisone group compared with acyclovir patients. The incidence of sequelae was the same in both groups. According to these results, in a 10-day treatment cycle acyclovir given 800 mg three times is not as useful as prednisone given 1 mg/kg of body weight once a day in patients with idiopathic facial nerve paralysis.