OBJECTIVE: To compare the efficacy and safety of valacyclovir hydrochloride and famciclovir for the treatment of herpes zoster. DESIGN: A double-blind, randomized, controlled, multicenter clinical trial in which patients received 7 days of treatment and were followed up for 24 weeks. SETTINGS: Patients reported directly to specialist centers or were referred from primary care centers. PATIENTS: There were 597 otherwise healthy immunocompetent outpatients, aged 50 years and older, who presented within 72 hours of onset of zoster rash. INTERVENTIONS: Treatment with valacyclovir hydrochloride (1 g 3 times daily) or famciclovir (500 mg 3 times daily) for 7 days. MAIN OUTCOME MEASURES: Resolution of zoster-associated pain and postherpetic neuralgia, rash healing, and treatment safety. RESULTS: Intent-to-treat analysis did not detect statistically significant differences for valacyclovir vs famciclovir on resolution of zoster-associated pain (hazard ratio, 1. 02; 95% confidence interval, 0.84-1.23; P =.84). Furthermore, no differences were evident between treatments on rash healing rates and on a range of analyses of postherpetic neuralgia. Safety profiles for valacyclovir and famciclovir were similar, with headache and nausea being the more common adverse events. CONCLUSIONS: Valacyclovir treatment is comparable to famciclovir treatment in speeding the resolution of zoster-associated pain and postherpetic neuralgia. Current wholesale prices indicate that valacyclovir is the more cost-effective treatment for herpes zoster ($83.90 vs $140.70 per course).