Significant mental health symptoms are reported in troops deployed to Iraq and Afghanistan (OEF/OIF). Symptomatic troops are more likely to be discharged and become eligible for Department of Veterans Affairs (DVA) care. Prevalence and predictors of mental health symptoms were assessed in 339 OEF/OIF veterans and reservists registering at the San Diego DVA. Participants completed self-report questionnaires assessing combat exposure, posttraumatic stress disorder (PTSD) symptom frequency and severity, depression, and substance and alcohol abuse. A minority of participants (36%) did not screen positive for mental health symptoms; the remainder met threshold for caseness of PTSD, depression, or substance and alcohol abuse. Using a hierarchical logistic regression model, gender, age, race, and rank were not significantly related to PTSD caseness, whereas most recent branch of service and report of injury during combat were. Follow-up analyses revealed that trauma history and combat exposure varied by branch of service. Knowledge of base rates and vulnerability factors can aid in rapid detection of "at risk" individuals.