PROJECT SUMMARY The proposed Telomere Research Network (TRN) will establish best practices related to telomere length (TL) measurement applicable to population-based studies and will define the extent to which TL can be effectively applied as a sentinel of aging-related disease risk and indicator of environmental and psychosocial stress exposure across the life span. Across scientific fields, the use of telomeres as a marker of exposure and a harbinger of disease risk and accelerated aging is expanding. The explosion of telomere research, while promising, has raised methodological and reporting concerns triggered by inconsistent reproducibility. To address these concerns and advance telomere research, this U24 proposes the following specific AIMS: 1) Create a living network of invested stakeholders to address challenges in determining the extent to which TL is a sentinel of environmental exposures, psychosocial stress, and disease susceptibility; and to ensure the highest rigor and reproducibility in current and future telomere studies. 2) Support and coordinate U01 efforts by ensuring seamless sharing of samples, data, and protocols and fostering interactive discussions focused on best practices for TL measurement. 3) Facilitate the infrastructure for sustained cross-discipline dialogue, dissemination, and research related to TL as a sentinel of cumulative exposure and a predictor of health and aging. To achieve these AIMS, the U24 proposes to recruit a diverse and interactive network of scientists invested in resolving methodologic concerns in TL metrics; engage in formal testing of the extent to which TL, telomerase and other telomere indicators serve as sentinels of age-related disease and cumulative exposures; and define best practices for TL measured in population studies. These AIMS will produce clear methodologic standards, pipelines for increased cross-study analyses and collaboration, and a sustainable platform for continued dialogue related to the measurement of TL and its implications for aging, exposure, and stress research.