The objective of this study was to evaluate the efficacy and safety of pregabalin in preventing relapse in generalized social anxiety disorder (SAD). Patients with Diagnostic and Statistical Manual of Mental Disorders (Fourth Edition) generalized SAD, who met responder criteria after 10 weeks of open-label treatment with fixed-dose pregabalin (450 mg/day; n=153), were randomly assigned to 26 weeks of double-blind treatment with pregabalin (450 mg/day) or placebo. The primary a-priori outcome of time to relapse was analyzed using the Kaplan–Meier method and the log-rank test. Double-blind treatment with pregabalin was associated with significant delay in time to relapse versus placebo (P=0.035), and with significantly greater maintenance of symptomatic improvement over 26 weeks on the Liebowitz Social Anxiety Scale total (P=0.012) and subscale scores and on the Marks Fear Questionnaire total phobia (P=0.010) and social phobia (P=0.014) subscales. Pregabalin was generally well tolerated. During the double-blind phase, the adverse events that occurred more frequently with pregabalin compared with placebo were dizziness (11.3 vs. 4.1%) and infection (21.3 vs. 16.4%). The results of this study suggest that pregabalin (450 mg/day) is safe, well tolerated, and has significant relapse-prevention efficacy over 26 weeks in patients with SAD who responded to an initial course of the pregabalin treatment.