The aim of the study was to examine the efficacy of valproic acid in participants with social anxiety disorder. Following a 2-week single-blind, placebo run-in period, 17 participants were enrolled in a 12-week open flexible-dose trial of valproic acid (500-2500 mg). The primary outcome measures were the mean change from baseline in the Liebowitz Social Anxiety Scale (LSAS) total score and responder status [defined as a Clinical Global Impression of Improvement score (CGI-I) < or =2]. Social anxiety symptoms as measured by the LSAS and CGI-I scores significantly improved with treatment. The mean reduction in the LSAS was 21.3 points in the last visit carried forward analysis and 19.1 points for the completer analysis, with 41.1% and 46.6% participants, respectively, achieving responder status. The results from this open-label trial suggest the potential efficacy of valproic acid for the treatment of social anxiety disorder. Placebo-controlled trials are indicated to confirm these findings.