BACKGROUND. Alcohol screening and brief alcohol counseling is ranked the 3rd highest prevention priority for the US. The VA is leading other health care systems in implementing brief alcohol counseling for patients with alcohol misuse and now needs a valid measure of whether drinking shows clinically meaningful changes after brief alcohol counseling in order to determine whether implementation efforts are having the intended effects. The proposed research will establish whether the AUDIT-C, a brief and valid screening instrument routinely used in the VA, can serve this purpose. OBJECTIVES. The proposed study evaluates the validity of changes in AUDIT-C scores among patients who initially screen positive for alcohol misuse. The proposed study will specifically: 1. Determine whether changes in AUDIT-C scores at follow-up alcohol screening are associated with changes in high density lipoprotein cholesterol (HDL), a laboratory test known to be a sensitive indicator of changes in alcohol consumption; 2. Determine whether changes in AUDIT-C scores at follow-up alcohol screening are associated with changes in adherence to medications used for chronic disease prevention; and 3. Evaluate whether resolution of alcohol misuse at follow-up is associated with a lower risk of VA care for trauma or acute alcohol-related gastrointestinal (GI) conditions in the following 12 months. METHODS. This cohort study uses data from the VA's Corporate Data Warehouse (CDW), National Patient Care Databases (NPCD), and Decision Support System (DSS). Eligible patients received care at one of 28 Western VA facilities in the CDW, were screened with the AUDIT-C questionnaire on two occasions at least one year apart between January 2004 and June 2007, and screened positive for alcohol misuse on their first AUDIT-C (estimated eligible 52,856). Aim 1 analyses evaluate the concurrent validity of changes in AUDIT-C scores by evaluating the association between changes in AUDIT-C scores and changes in HDL cholesterol. Aim 2 analyses evaluate whether changes in AUDIT-C scores are associated with changes in medication adherence based on prescription refill data. Aim 3 analyses evaluate whether patients who resolve alcohol misuse based on follow-up AUDIT-Cs have lower risk for two acute alcohol-related medical conditions (trauma and GI hospitalizations) compared to those who do not resolve alcohol misuse on follow-up AUDIT-Cs. IMPORTANCE TO VA: If the AUDIT-C is a valid measure of changes in drinking over time, annual AUDIT-C assessments already implemented in VA could be used by VA clinicians, quality leaders, and implementation researchers to evaluate the effectiveness of brief alcohol counseling.