Behaviorally HIV-infected youth (ages 12-24) account for 14% of known incident HIV infections in the U.S., with significant numbers of youth meeting criteria for HAART initiation. Successful HAART outcomes are complicated by the cognitive and psychosocial challenges facing youth. For youth, treatment interventions need to consider the entire psychosocial, biologic, structural, and behavioral context of the patient in order to assure that interventions will prove both effective and efficacious. Our prior data has shown that 40% of HIV-infected treatment-eligible youth in a clinical cohort did not receive HAART at any point during the study period, which suggests that there are likely patient and provider barriers to HAART initiation that need to be deciphered. The goal of this proposed CDA is to examine provider and patient factors that contribute to the offering of and acceptance of treatment in youth. Such an understanding is vital to the development and implementation of clinically-relevant trials of behavioral and treatment interventions that reflect the unique features of caring for HIV-infected youth. To accomplish this, with the guidance of my mentoring team, I will embark on four inter-related projects: (1) I will perform a retrospective cohort analysis to assess the impact of age on HAART initiation for treatment-eligible patients in the multi-site HIV Research Network; (2) through a detailed examination of demographic, clinic data, and ACASI-acquired data on mental health, substance abuse, patient-provider and patient-clinic interactions, I will examine patient predictors of HAART initiation. (3) I will assess factors impacting provider clinical decision-making regarding HAART initiation in treatment-eligible youth through semi-structured interviews; and (4) I will evaluate the relationship between provider demographics, training, beliefs, knowledge, and attitudes and HAART initiation in treatment-eligible youth in a large multi-site cohort of providers. Through these projects, I will examine the lower HAART initiation rates in HIV-infected youth and examine patient and provider decision- making and barriers to HAART initiation that will inform targeted clinical and biomedical interventions for this population. Through the training plan, I will acquire the understanding of behavioral theory, survey methodology, health services research, and analysis to complete the proposed projects and to inform my future projects. The structured mentoring and guidance will enhance my development into a trans-disciplinary independent researcher capable of effectively designing, studying, and implementing relevant, feasible, high impact interventions, clinical algorithms, and treatment strategies that improve HAART initiation and outcomes for HIV-infected youth. Narrative: The numbers of U.S. youth becoming infected with HIV is increasing. HAART has many benefits; however, HIV-infected youth who meet treatment criteria have lower rates of HAART utilization than traditionally reported for adults. It is essential to understand both patient and provider decision-making regarding initiating HAART in youth in order to inform effective and acceptable targeted interventions and strategies to improve HAART initiation rates and ultimately outcomes in HIV-infected youth.