Section GROWTH and DEVELOPMENT LONGITUDINAL COHORT STUDY OF GROWTH, DEVELOPMENT, PUBERTY AND REPRODUCTIVE HEALTH IN RUSSIAN BOYS Sergeyev Oleg 1,2 Revich Boris6 , Lam Thuy3 , Dikov Yury1 , Williams Paige L.4 , Sergeyeva Lyubov1 1Chapaevsk Medical Association, Chapaevsk, Russia 2Vavilov Institute of General Genetics, Moscow, Russia 3Department of Environmental Health, Harvard School of Public Health, Boston, USA 4Departments of Biostatistics and Epidemiology, Harvard School of Public Health, Boston, USA 5Channing Division of Network Medicine, Department of Medicine, Brigham and Women’s Hospital, Boston, USA 6Institute of Forecasting, Russian Academy of Sciences, Moscow, Russia 7 Pediatric Endocrine Division, Departments of Pediatrics and Cell and Developmental Biology, University of Massachusetts Medical School, Worcester, USA Introduction. <...> There are few longitudinal male cohort studies with serial assessments of growth and puberty. <...> We assembled a multi-disciplinary team of U.S. and Russian researchers to design and conduct a longitudinal boys’ cohort study of male growth, development, puberty and reproductive health in Chapaevsk, Russia. <...> At annual study visits scheduled at each subject’s birth month, the same study physician (O.S.) assesses pubertal staging and one nurse (L.S.) measures anthropometric variables. <...> Pubertal assessments are based on a 1–5 scale for genitalia and pubic hair staging by visual inspection, testicular volume is measured using orchidometers, and penile length is measured with a ruler. <...> Blood and urine samples for hormonal, chemical, genetic and epigenetic analysis were collected at baseline and biennially. <...> In 2003–2005, 516 prepubertal boys were recruited at ages 8–9 years (86% of all eligible Chapaevsk boys) to be followed annually for at least 10 years. <...> The participation rate has remained high with over 75% followed for 6 years and 64% at 9 years of follow-up with 4319 visits as of February 2014. <...> A core set of 23 anthropometric indices measured at annual visits (e.g., height, weight, segment lengths and diameters, circumferences, skinfolds) are available, as well as an additional 30 measures conducted biennially. <...> Longitudinal curves for selected anthropometric and pubertal measures will <...>