ABSTRACT This is a response to PA-18-591: Administrative Supplements to Existing NIH Grants and Cooperative Agreements (Parent Admin Supp Clinical Trial Optional). This parent project is part of the Intensive Longitudinal Health Behaviors Network (ILHBN) established to collaboratively study factors that influence dynamic health behaviors in individuals’ daily lives, using intensive longitudinal data (ILD) collection and novel analytic methods. The network includes seven U01 projects and one U24 Research Coordinating Center (RCC). This specific project leverages ILD in a genetically informative design to understand the development of affect, mobility, and drug use in the context of the COVID-19 pandemic. Evidence suggests that the experience of the COVID pandemic has caused increases in depressed mood and anxiety. These, in turn, have implications for other health behaviors, such as substance use behaviors. Using intensive longitudinal data, we will evaluate the nature and etiology of how individuals’ self-report affective dynamics and mobility patterns vary over time, using phone-based location data to infer individuals’ activity space (typical area traveled for routine everyday activities) as well as local covid conditions (e.g., case counts, lockdown policy) related to COVID. We will test whether changes in local covid conditions are associated with each other and with changes in affect, mobility, and substance use. Data from the parent project will be shared with the ILHBN Research Coordinating Center to facilitate scientific efforts in other ILHBN studies.