This paper considers the tracking of physical activity during childhood, adolescence, and adulthood in the context of issues relaled to adherence. Based upon two comprehensive literature reviewers and allowing ihr differences in measures of physical activity, the available data are generally consistent in showing moderate tracking of physical activity during childhood and adolescence and more variable but lower levels of tracking across longer intervals within adolescence and horn adolescence into young adulthood. Data relating childhood and adolescent activity to activity at older apes in adulthood are not extensive but suggest a relatively weak association. Factors that influence physical activity are many, and studies of tracking do not include these correlates or covariates. Adherence to a program of physical activity on a regular basis is viewed as important for the health of individuals and the population. Adherence research tends to focus on the adoption of physical activity, the maintenance of regular activity, and barriers to activity or an active lifestyle. This research is based almost exclusively on adults given the association between physical in activity, i.e., a sedentary lifestyle. on the risk of morbidity and mortality from several diseases, and the beneficial effects of a lifestyle of regular physical activity on the efficient function of various bodily systenls. weiaht maintenance, reduced risk of several degenerative diseases. reduced risk of mortality, and overall improvement of quality of life (Bouchard, Shephard & Stephens. 1994).