The purpose of this study is to (1) compare the response of civilians with Posttraumatic
Stress Disorder(PTSD) currently receiving sertraline without an optimal response to
risperidone augmentation vs. placebo, and (2) to evaluate the tolerability of risperidone
augmentation, and (3) to identifiy predictors of response to risperidone augmentation. the
hypothesis is that risperidone augmentation of sertraline treatment of PTSD is safe and
effective.