OBJECTIVES The purpose of this study was to evaluate the relative efficacy and safety of pregabalin and clonazepam in the treatment of anxiety disorders. METHODS A meta-analysis was performed with randomized clinical trials (RCTs) where pregabalin or clonazepam were used for any anxiety disorders. Effectiveness was assessed with the Hamilton Anxiety Rating Scale(HAM-A); safety with the frequency and type of adverse events(AEs). RCT were searched in July 2008 in Medline, EMBASE, PsycInfo, CINAHL and the Cochrane Collaboration. Two independent reviewers identified the abstracts, full articles, and then extracted data; results were compared and settled through consensus. RCT included both drugs and its comparison with placebo. Odds ratios and weighted means differences(WMD) were calculated. Both, fixed and random effects models were employed in the analysis. RESULTS From 1893 abstracts, we obtained 40 RCT, 23 were excluded (unacceptable designs, insufficient outcome data, no placebo control) leaving 17. Seven pregabalin studies were used to evaluate its effectiveness and safety; four clonazepam studies for effectiveness and six for safety. Clonazepam studies included panic disorder and social phobia. Six of seven pregabalin studies were in generalized anxiety disorder and one for social anxiety disorder. We found that both drugs significantly diminished anxiety levels after four to 32 weeks of treatment. Among clonazepam studies the frequency of AEs was higher than placebo by nearly 50%; with pregabalin, less than 30%. We didn't found any head-to-head studies with pregabalin and clonazepam and no statistical difference in anxiety level reduction was distinguished between drugs, WMD in HAM-A: 1.2(CI95% -1.13, 3.54).However, clonazepam showed higher AE rates than pregabalin in somnolence(OR 0.54; 95%CI 0.44-0.66), headache(OR 0.50; 0.34-0.74), blurred vision(OR 0.36; 0.13-0.98) and cognitive impairment(OR 0.25; 0.09-0.72). CONCLUSIONS Clonazepam and pregabalin are effective in diminishing anxiety levels in several anxiety disorders, although clonazepam seems to cause a higher frequency of AEs.