Abstract-A systematic review of the literature on postherpetic neuralgia was performed. The authors identified studies using the National Library of Medicine's Medline database and Cochrane Library database. The authors determined absolute reduction rate, number needed to treat (NNT), 95% CI for NNT, and number needed to harm (NNH) for successful therapies of postherpetic neuralgia. Tricyclic antidepressants, gabapentin, pregabalin, opioids, and lidocaine patch were found to be effective in reducing the pain of postherpetic neuralgia. NEUROLOGY 2004;63:959 -965 Acute herpetic neuralgia is characterized as burning, aching, electric shock like pain, or unbearable itching in association with the outbreak of a herpes zoster rash. The pain is associated with dysesthesias, paresthesias, hyperalgesia, hyperesthesia, and allodynia (production of pain by innocuous stimuli).1 The pain may precede the onset of the herpetic rash and, rarely, herpetic neuralgia can occur without the development of a rash.2 Postherpetic neuralgia, persistence of the pain of herpes zoster more than 3 months after resolution of the rash, is relatively common, affecting 10 to 15% of those with herpes zoster. Zoster-associated pain is used to describe the continuum of pain from acute herpes zoster to the development of postherpetic neuralgia. The time interval used in the clinical case definition of postherpetic neuralgia varies in the literature from 1 to 6 months after resolution of the rash. The incidence of postherpetic neuralgia increases with age. 3 The duration of postherpetic neuralgia is highly variable. In a longitudinal study, of those who developed postherpetic neuralgia, only 48% were symptomatic 1 year after onset.4,5 A prospective study of postherpetic neuralgia, performed through a network of primary care providers in Iceland from 1990 to 1995, showed that 14 of the 25 who developed postherpetic neuralgia were symptomatic 12 months after onset.6 Thus, the natural history of resolution of postherpetic neuralgia over time is a confounder in the evaluation of treatment efficacy and may limit the ability to generalize the results of controlled clinical trials in this population.Administration of antiviral agents within 72 hours of the onset of herpes zoster can reduce the intensity and duration of acute illness, and can prevent postherpetic neuralgia, 7 as may the use of amitriptyline.8 Efforts at prevention of herpes zoster and postherpetic neuralgia are important in that 40 to 50% of those with postherpetic neuralgia do not respond to any treatment. 9 The treatment of acute herpes zoster 10 and the prevention of postherpetic neuralgia are beyond the scope of this parameter.This practice parameter was developed to answer the following clinical question: In patients with postherpetic neuralgia, which treatments provide benefit in terms of decreased pain and improved quality of life?Process. We searched the National Library of Medicine's Medline database and the Cochrane database for peer-reviewed articles published between