Adrenal gland consists of cortex and medulla. Cortex secretes steroidal hormones and Medulla secretes adrenaline and noradrenaline. Cortex is divided in three zones, i.e. zona glomerulosa, zona fasciculata, and zona reticularis. Chronic deficiency of adrenocortical hormones leads to Addison’s disease. Adrenocortical hormones are more necessary than medullary hormones. Mineralocorticoids are more important than glucocorticoids. This chapter aims to present a brief discussion on structure, synthesis and release of corticosteroids, it then briefly gives pharmacokinetics of corticosteroids, followed finally by the mechanism of action of corticosteroids.