The aim of this article was to review the literature on the youth predictors of physical activity in adulthood. The outcome measure in the reviewed studies was the level and types of physical activity at adult age. The youth predictors here included different measures of physical activity, health and fitness as well as some social and behavioral variables measured in childhood or in adolescence. The goal was to identify the elements in youth that are associated with a high level of physical activity in adulthood. This information can be used by health promoters who plan physical activity programs for young people to enhance lifelong physical activity. This literature review is also addressed to researchers to provide ideas for further studies in this area.