Post-traumatic stress disorder (PTSD) is a prevalent and disabling disorder. Recognition of neurobiological abnormalities associated with this condition suggests the potential efficacy of medication in its treatment. Nevertheless, questions regarding the efficacy of medications remain, despite general endorsement by clinical practice guidelines of selective serotonin reuptake inhibitors (SSRIs) as first-line agents in treating PTSD. This paper reviews evidence from randomized controlled trials (RCTs) for the efficacy of acute and long-term pharmacotherapy for PTSD, including the treatment of refractory PTSD. In addition, we conducted a systematic meta-analysis to compare the efficacy of different medications in treating PTSD. The effects of methodological study features (including year of publication, duration, number of centres) and sample characteristics (proportion of combat veterans, gender composition) were also tested. The largest body of evidence for short- and long-term efficacy of medication currently exists for SSRIs, with promising initial findings for the selective noradrenergic reuptake inhibitor venlafaxine and the atypical antipsychotic risperidone. Treatment effect was predicted by number of centres and recency of the study, with little evidence that sample characteristics predicted response. Evidence for the effectiveness of benzodiazepines is lacking, despite their continued use in clinical practice. Finally, the α1 antagonist prazosin and the atypical antipsychotics show some efficacy in treatment-resistant PTSD. Adequately powered trials that are designed in accordance with best-practice guidelines are required to provide conclusive evidence of clinically relevant differences in efficacy between agents in treating PTSD, and to help estimate clinical and methodological predictors of treatment response.