AbstractAdrenocortical insufficiency may arise through primary failure of the adrenal glands or due to lack of ACTH stimulation as a result of pituitary or hypothalamic dysfunction. Prolonged administration of exogenous steroids will suppress the hypothalamic–pituitary‐adrenal axis, and hence cortisol secretion. We review briefly the causes, investigation, and treatment of adrenal insufficiency, and highlight aspects of particular relevance to patients with adrenal tumors. J. Surg. Oncol. 2012; 106:595–599. © 2012 Wiley Periodicals, Inc.