This project addresses three important research questions. First, adolescents and young adults (AYA) with sickle cell disease (SCD) and their parents/caregivers will be engaged to inform the (1) domains of health-related quality of life (HRQOL) most important to them, (2) frequency at which they are willing to complete them, and (3) other procedures related to the use, uptake and effect of the HU-Go app as a tool to improve hydroxyurea (HU) adherence. Second, this study seeks to utilize novel modern mobile technology using a multi-functional personalized platform to improve adherence to HU and measure HRQOL in youth with SCD, using NIH-endorsed PROMIS® measures, based on a conceptual model with predefined behavioral targets and mediators. Third, we plan to assess HRQOL changes and identify modifiable behavioral strategies that could serve as surrogates or predictors for HU adherence. This real-time feedback might empower self-directed changes in behavior that could improve adherence to HU.