Although many pain treatments have similar effects on global measures of pain intensity or unpleasantness, a growing body of evidence suggests that different treatments have differential effects on specific qualities or domains of pain. Knowledge about the effects of different treatments on specific pain qualities could help determine similarities and differences in the mechanisms of action of pain treatments, as well as help clinicians to target pain treatments to the most appropriate individuals or conditions. We performed secondary analyses on data from a randomized, double-blind, placebo-controlled trial of Gabapentin Extended Release (G-ER) in patients with postherpetic neuralgia (PHN) to identify the effects of this treatment on overall pain and specific pain qualities. Patients were titrated to their assigned treatment (G-ER 1800 mg/day dosed either once- or twice-daily or placebo) over 2 weeks and remained at that dose for an additional 2 weeks. Results of the primary analysis showed significant differences between G-ER twice-daily and placebo for reductions from baseline in average daily pain score (p=0.014), average daily sleep interference score (p=0.006), and an average of 10 items on the Neuropathic Pain Scale (NPS; p=0.019). There was also a trend towards significant differences between G-ER once-daily versus placebo for changes in these measurements. Secondary analyses indicated that G-ER, especially when administered twice-daily, had the greatest effects on sharp, dull, sensitive, and itchy pain, with significant differences between G-ER twice-daily and placebo for changes from baseline in NPS scores for these parameters. These findings provide support for the potential importance of assessing specific pain qualities as outcomes in clinical trials. If replicated in other samples, the findings may also be used by clinicians to identify those patients for whom G-ER may be particularly effective; i.e., patients with PHN presenting with pain that they describe as sharp, dull, sensitive, or itchy.