Once HAART has been initiated, participants will be expected to be assessed at weeks 1,2,3,4,6,8,10,12,14, and 16. Detailed adherence and dispensing records for all antiretroviral medications for each participant will be maintained. Adherence will be assessed primarily on the basis of pharmacy refill records, as well as self-report. Subsequently participants will attend monthly clinical follow-up visits at weeks 20, 24, 28, 32, 36, 40, 44, 48, and 52. Standard laboratory monitoring will be performed at that time, and will include complete blood count (CBC), differential, basic chemistry, liver and kidney profile, as well as CD4 cell count and plasma HIV-1-RNA level, consistent with current care guidelines. All patients will also undergo urine toxicology screens at baseline and quarterly (weeks 12, 24, 36, and 52) in order to assess any effects of engaging in HAART programs on substance use. Follow-up will also include an adverse events assessment (ADE) from a standardized list of signs and symptoms noted by either the patient or practitioner or identified through laboratory testing. At baseline and each quarterly visit, participants will complete the Center for Epidemiologic Studies Depression Scale (CES-D) where a score of 16 correlates with risk of depression. This tool has been validated in our population in a prior study. Participants will also complete the Addiction Severity Index questionnaire, a validated instrument used to examine severity of psychosocial problems in seven domains including drug and alcohol use . Composite scores are derived, and higher scores reflect greater problems. Past 3-month versions of the HIV Risk Behavior Scale will also be administered at baseline and at quarterly visits. This scale assesses injection drug use and sexual behaviors, and responses are coded on a 6-point scale with higher values indicating higher risk.

Participants who are randomized to receive a reinforcer for clinic follow-up will receive the reinforcer at the end of each clinic visit. When the reinforcer is linked to plasma viral load, subjects in the reinforcer arm will be notified within a week of the plasma viral load result, and of any reinforcement earned. Subjects can elect to come in at any time to receive the reinforcement, or they can wait until their next monthly appointment and receive the earnings at that time.

For participants who do not present for laboratory and clinical follow-up within two weeks on either side of their scheduled quarterly visit, an extensive investigation into the client's whereabouts through street outreach as well as a search of hospital records for hospitalization and the provincial vital statistics database for possible deaths will be prompted. Those who discontinue therapy or who are lost to follow-up at or before 52 weeks will be considered therapy failures in the analyses.

A final visit 24 weeks after the week 52 visit will be performed. This will involve the same procedures as the quarterly study visits during the first year, including standard laboratory tests and urine toxicology, ADE assessments, and CES-D, Addiction Severity Index and HIV Risk Behavior Scale questionnaires. Participants who fail to present for laboratory and clinical follow-up within 2 weeks of the expected date of this visit will be sought as described above.