Emerging data suggest that second-generation antipsychotics such as aripiprazole may be effective in the treatment of post-traumatic stress disorder (PTSD). However, few clinical trials have used aripiprazole in PTSD, and data are limited on its use in Veterans with PTSD. The objective of this pilot trial was to investigate the safety and efficacy of aripiprazole in Veterans with PTSD. Ten individuals (five men and five women) meeting the Diagnostic and statistical manual of mental disorders, 4th ed., PTSD criteria participated in this 12-week, open-label, flexibly dosed monotherapy trial. The dose range of aripiprazole was 5-30 mg/day, titrated to tolerability and clinical response. The primary outcome measure was the Clinician-Administered PTSD Scale. Additional outcomes included the Short PTSD Rating Interview, the Treatment Outcome PTSD Scale (Top-8), the Davidson Trauma Scale, the Positive and Negative Syndrome Scale, the Beck Depression Inventory-Fast Screen, and Clinical Global Impressions-Improvement. Eight participants completed the study, and aripiprazole was generally well tolerated and associated with a significant improvement in PTSD symptoms, as measured by the Clinician-Administered PTSD Scale (primary outcome measure) and by the Short PTSD Rating Interview, the Treatment Outcome PTSD Scale, and the Davidson Trauma Scale. An improvement was also observed on all three Positive and Negative Syndrome Scale subscales and the Beck Depression Inventory-Fast Screen, and the average Clinical Global Impressions-Improvement ratings indicated that patients were 'much improved'. These promising initial results merit further investigation in a larger, randomized-controlled trial.