Seven published, randomized, placebo-controlled clinical trials with pregabalin have shown robust efficacy for relief of neuropathic pain from DPN and PHN. An investigation of the efficacy and safety of twice daily pregabalin enrolled 395 adults with painful DPN for > or = 1 year in a 12-week, double-blind, placebo-controlled trial. Patients were randomized to placebo, 150, 300, or 600 mg/day pregabalin (n = 96, 99, 99, and 101). Primary efficacy measure was change from baseline in endpoint mean pain score from patients' daily pain diaries. Secondary efficacy measures included pain-related sleep-interference scores, Patient and Clinical Global Impressions of Change (PGIC, CGIC), and the EuroQOL Health Utilities Index (EQ-5D). Statistically significant reduction in pain was observed in patients receiving pregabalin 600 mg/day, and 46% of patients treated with 600 mg/day pregabalin reported > or = 50% improvement in mean pain scores from baseline (vs 30% of placebo patients, p = 0.036). Number needed to treat to achieve such response was 6.3. Pregabalin 600 mg/day was significantly superior to placebo in improving pain-related sleep-interference scores (p = 0.003), PGIC (p = 0.021), and CGIC (p = 0.009). (Neither pregabalin 150 nor 300 mg/day separated from placebo on these measures, largely because of an atypically large placebo response in one country representing 42% of patients.) All pregabalin dosages were superior to placebo in improving EQ-5D utility scores (all p > or = 0.0263 vs placebo). Pregabalin was well tolerated at all dosages; adverse events were generally mild to moderate. Number needed to harm (discontinuation because of adverse events) was 10.3 for pregabalin 600 mg/day.