We are testing the idea that mifepristone, which blocks the effect of the hormones progesterone and cortisol, will help treat PTSD. Progesterone is a hormone made in the bodies of both men and women and its main role is in regulating the menstrual cycle and in pregnancy. Cortisol is also a hormone made in the body of both men and women and helps the body respond to stress. Cortisol also has a role in making emotional memories more intense than other memories. We are testing whether blocking the effect of cortisol with mifepristone as you recall your trauma may be able to decrease the intensity of your traumatic memories. This medication will not completely block out your memories of the traumatic experience but may decrease how much your thoughts are drawn back to the memory of the traumatic event.