This study examined the impact of participation in the Department of Veterans Affairs (VA) disability system on health care use by veterans filing disability claims on the basis of posttraumatic stress disorder (PTSD). VA administrative databases were used to examine health care use in 3-month intervals before; during, and after veterans' filing of PTSD disability claims. Subjects were all veterans using some VA health care who filed PTSD claims between 1997 and 1999 in a large Midwestern region. PTSD claimants used more medical and mental health services after filing a disability claim, compared with the preapplication period. Continuation of elevated mental health care use after claim determination occurred only for those veterans whose claims were approved. Use of VA mental health care before the disability examination was associated with an increased likelihood of claim approval. For veterans with PTSD, disability system participation may both promote and be promoted by receipt of mental health care.