Key PointsQuestionIs there evidence of a signal for clinical efficacy for the glucocorticoid receptor antagonist mifepristone in the treatment of male veterans with posttraumatic stress disorder?FindingsIn this randomized clinical trial of short-term mifepristone treatment (600 mg per day for 7 days) in 80 male veterans with posttraumatic stress disorder (41 receiving mifepristone and 39 receiving placebo), the difference in the clinical response rate to mifepristone vs placebo at 4 and 12 weeks was less than the predefined clinical margin used to define efficacy.MeaningThese results do not support an indication for a phase 3 trial of this regimen in this heterogeneous population.