 The CATS project is designed to increase understanding of interventions that are feasible and effective in helping injection drug users IDU or other patients at high risk of poor medication adherence who are HIV-positive to maintain a high ART adherence. The study will involve: assessing the feasibility and acceptability of using real-time feedback, a wireless technology-updated adaptation of an approach the investigators found to be feasible and effective in China, to promote ART adherence among Chinese patients, including IDU; generating preliminary effectiveness data of real-time feedback on adherence, CD4 count, and HIV viral load; and identifying the factors that explain how real-time feedback influences intervention success or failure. 