Study Abstract: It is suspected, but not well documented, that persons with severe mental illness represent a significant transmission source of serious infectious diseases. SMI diagnoses are defined as schizophrenia, schizoaffective disorder, bipolar disorder, or posttraumatic stress disorder (PTSD). Severely mentally ill persons are at high risk for Human Immunodeficiency Virus/Acquired Immunodeficiency Syndrome (HIV/AIDS). To assess the risk of HIV and related infections among these individuals, the National Institute of Mental Health (NIMH) Office on AIDS funded the HIV/SMI five site collaborative study "Assessing HIV/AIDS and Associated Health Risks in People with Severe Mental Illness". This Durham ERIC study supplements the NIMH HIV/SMI study with a four-year longitudinal cohort study of 300-plus SMI veterans in order to estimate the prevalence of HIV risk behaviors and HIV infection, as well as to measure utilization of health services over time. The Durham VA is the only VA site represented in the study and is collaborating with four non-VA sites including Dartmouth, University of New Hampshire, University of Connecticut and Duke University. As such, we have the additional goals of investigating health and health-care-service issues relevant to veterans with SMI and of establishing a database for the longitudinal study of veterans with SMI.