To achieve these objectives, the investigators propose to conduct a Phase IIa, multi-site, double-blind, placebo controlled trial of mifepristone in Veteran outpatients with military-related PTSD through the VA's Cooperative Clinical Trial Award program. The investigators propose to enroll 90 unmedicated male Veterans with military related PTSD at four VA sites (Salisbury, NC, Bronx, NY, Durham, NC, and San Diego, CA). Eligible Veterans will be randomly assigned in parallel groups to treatment with 600 mg/day mifepristone or placebo for one week and followed for up to three months. In this initial trial the investigators propose to study the effects of mifepristone in Veterans with PTSD as monotherapy, rather than as an adjunctive treatment, in order to better detect a signal if there is one.