Motivational Enhancement System for Adherence

Inclusion Criteria: Phase I \& II, all participants * Engaged in care at the enrolling AMTU; * HIV-1 infection documented by a positive result on any of the following licensed tests at any time: any HIV-1 antibody test confirmed by Western blot, HIV-1 culture, HIV-1 DNA PCR, or plasma HIV-1 RNA PCR \> 1,000 copies/ml; * Age 16 to 24 years, inclusive at the time of enrollment; * Naïve to antiretroviral therapy; NOTE: Females who have received antiretroviral therapy for the sole purpose of preventing maternal to child transmission (MTCT) will be considered antiretroviral naïve. * Ability to understand written and/or spoken English; * Willingness to provide signed informed consent/assent in either English or Spanish; and * Parental or legal guardian permission, if warranted. Phase I MESA Participants/Phase II All Participants - Recommended by a health care provider to start HAART for treatment of HIV-1 infection within the 12 weeks prior to protocol screening. Phase I MESH Participants \- Not recommended by a health care provider to start HAART for treatment of HIV-1 infection. Exclusion Criteria: Phase I \& II, all participants * Known pregnancy (pregnancy testing is not required); * Inability to understand spoken or written English; * Visibly distraught and/or visibly emotionally unstable (e.g., exhibiting suicidal, homicidal, manic or violent behavior); * Active drug or alcohol use or dependence that, in the opinion of the site personnel, would interfere with ability to give true informed consent and to adhere to the study requirements; * Active psychiatric condition that in the opinion of the site personnel, would interfere with the ability to give true informed consent and to adhere to the study requirements; * Acute illness that, in the opinion of the treating clinician, would interfere with the participant's ability to adhere to the protocol requirements and/or interfere with the protocol objectives; and * Concurrent participation or participation within the previous 4 weeks, in any behavioral intervention study or program, including, but not limited to, ATN 069 and ATN 073. Permission to co-enroll into other behavioral studies or programs must be obtained from the protocol chair or designee. Phase II, All Participants Prior participation in the Phase I MESA intervention (Phase I MESH control participants are eligible to participate).