The present study sought to identify posttraumatic stress disorder (PTSD) patients at high risk for negative behavioral outcomes (violence, suicide attempts, and substance use). The Mississippi Scale for Combat-Related PTSD, the Beck Depression Inventory, and demographic and behavioral data from 409 male combat veterans who completed a VA residential rehabilitation program for PTSD were analyzed using signal detection methods (receiver operating characteristics). A validation sample (N = 221) was then used to test interactions identified in the signal detection analyses. The best predictors of behaviors at follow-up were those same behaviors shortly before intake, followed by depressive and PTSD symptoms. However, for each of the models other than that for hard drug use, cutoffs determined at the symptom level did not lend themselves to replication. Recent high-risk behaviors, rather than patients’ history, appear to be more predictive of high-risk behaviors postdischarge.