Exposure of adipocytes to glucocorticoid hormones in vitro causes inhibition of glucose transport and metabolsim. Maximal inhibition of glucose oxidations is reduced from 42-50 to 22-25 to 5-8% in young, mature, and senescent rat adipocytes, respectively. Percent values also reflect absolute reductions since basal levels of glucose oxidation per cell are constant at all ages. Adipocytes of CD strain rats continue to increase in size throughout their lifespan, while cell size remains constant during the latter 80% of the Wistar adipocyte lifespan. Thus, cellular age, as well as possibly size, seems to be associated with these changes since they occur in adipocytes of both strains. Concentrations as well as absolute numbers of presumptive glucocorticoid receptors per cell are progressively reduced during maturation and aging of adipocytes in both rat strains. Glucocorticoid effects are known to require about 2 h and can be blocked by various antimetabolites during this period, reminiscent of classical steroid receptor-mediated responses. Thus, gradual loss of glucocorticoid receptors from adipocytes during maturation and aging may be related to progressively decreased glucocorticoid responsiveness.