PROJECT SUMMARY/ABSTRACT The goal of the second phase (2023-2030) of the Environmental influences on Child Health Outcomes (ECHO) Program is to extend and expand the ECHO Cohort to further investigate the impact of a broad range of early social and biological exposures during the preconception period and into young adulthood, on ECHO’s five key child health outcomes among diverse populations. Our pediatric ECHO cohort, ELGAN-ECHO, proposes to continue to: (1) lead collaborative ECHO Cohort science, (2) follow up existing ECHO Cohort participants, and (3) implement the ECHO Cohort Data and Biospecimen Collection Protocol. The broad goals of this proposal are to: (1) evaluate predictors of exposure to environmental stressors (chemical and non-chemical) during preconception, pregnancy, and early childhood; (2) identify factors that have the potential to modify the relationships between environmental exposures, perinatal biomarkers of inflammation (e.g., epigenetic, genomic and proteomic) and neurodevelopmental outcomes as our proposed specialty outcome area; and (3) maximize retention of diverse ELGAN participants. We will bring specialized expertise in environmental epidemiology related to metals, placental epigenetics, antecedents and correlates of preterm birth, and neurodevelopmental outcomes to the proposed project. In the first two years of the project (the UG3 phase) investigators from the ECHO-ELGAN team will collaborate with the ECHO Program to collaborate on the development of the ECHO Cohort Protocol for the preconception period and harmonization of data; lead and participate on ECHO committees, working groups, and task forces; plan participant follow-up, obtain approval for conducting the ECHO Cohort Protocol with oversight from the ECHO Cohort Consortium’s single IRB; reconsent existing ECHO Cohort participants; implement the ECHO Cohort Protocol for collection of data and biospecimens specified in that protocol; use the central data capture system to populate the ECHO Cohort Data Platform; retain study participants with an emphasis on diverse populations; and produce and disseminate ECHO Cohort science through publications and other public presentations. In the following five years (the UH3 phase) we will expand development, production, and dissemination of ECHO Cohort science, and continue to lend expertise on maintaining high retention rates and fidelity to the ECHO Cohort Protocol. Our over-arching perspective will be solution-oriented research questions that take advantage of the large sample size, diversity, and longitudinal nature of the ECHO Cohort and have potential to influence practices, programs, and policies to improve children’s health.