This project consisted of two phases. In Phase 1, we conducted clinical interviews (CAPS) assessing PTSD with 474 patients participating in the VHS at 1-year follow-up (T12). This phase validated a brief 17-item self-report PTSD screening measure (PCL-C) against a PTSD clinical interview diagnosis. We used the results of this validation study to estimate the prevalence of PTSD in VA primary care, and to propose the use of a brief measure (PRIME-MD) as a screen for PTSD in primary care. In Phase 2, we used the PCL-C to examine the impact of PTSD on health status and health care use. We tested the hypotheses that (a) PTSD has a direct effect on health status that is independent of the effects of comorbid medical conditions, depression, and alcohol use, and (b) that controlling for comorbid medical conditions, depression and alcohol use, PTSD has both a direct effect and an indirect effect (through health status) on health care utilization. These hypotheses are being tested using structural equation methods. If, as hypothesized, PTSD exerts direct and indirect effects on health services use, then both quality of care and efficiencies in health services delivery can be improved through appropriate detection, referral, and treatment of PTSD among patients in VA ambulatory care.