Glucocorticoids have been used in clinical oncology for more than three decades. Their anti-inflammatory action plays a major role in their clinical applications in oncology. The incidence and severity of side effects depend on the total dose and the duration of therapy, but optimal dosages for these drugs have not been determined. Little is known about other risk factors for toxicity. Prednisone and dexamethasone, the two most commonly used drugs, are well absorbed orally and share quantitatively similar pharmacokinetic values. No definite relationship is known between the glucocorticoid blood level (total and unbound concentration) and therapeutic effect. Glucocorticoids play a major role in the treatment of lymphoproliferative disorders and breast cancer, and they often succeed in palliating common symptoms in advanced cancer.