© 2015, Copyright © Taylor & Francis Group, LLC. One of the critical issues in HIV patients with substance use disorders is engagement in care. The authors measured engagement as adherence to comprehensive primary care that included primary routine care, mental health, sick call, research clinic visits, and laboratory visits in 189 HIV patients of an urban clinic in the southern United States. Substance users were highly engaged in care, but adherence to primary routine care and mental health appointments declined over time. While this finding warrants further scrutiny, social services should be aware of substance users' engagement in all aspects of primary care and provide support to facilitate it.