 This study is a randomized clinical trial with two treatment conditions: 1 onsite primary care in the Addictions Treatment Center ATC; experimental; or 2 referral primary care in the General Internal Medicine Clinic GIMC; control. Subjects are assessed at baseline and at 3, 6, and 12-month time points. The sample includes 720 veterans, newly presenting or returning to SUD treatment, who exhibited a chronic medical condition at screening, did not have a primary care provider; and did not present with a serious medical condition requiring ongoing care in three or more organ systems. Medical status outcome measures include scores on the SF-36, and total emergency room visits and medical or surgical inpatient admissions. Substance abuse outcomes are measured by treatment retention, changes in Addiction Severity Index ASI scores, and self-reported alcohol use. Lastly, overall VA health care costs per subject per the 12-month period following randomization are compared across groups. The main analysis involves intent-to-treat analysis of group onsite vs. referral by time 3, 6, 12-month using random effects regression models. 