Evaluation of endocrine issues is a sometimes overlooked yet important component of the preoperative medical evaluation. Patients with diabetes, thyroid disease, and hypothalamic-pituitary-adrenal axis suppression are commonly encountered in the surgical setting and require unique consideration to optimize perioperative risk. For patients with diabetes, perioperative glycemic control has the strongest association with postsurgical outcomes. The preoperative evaluation should include recommendations for adjustment of insulin and noninsulin diabetic medications before surgery. Recommendations differ based on the type of diabetes, the type of insulin, and the patient’s predisposition to hyperglycemia or hypoglycemia. Generally, patients with thyroid dysfunction can safely undergo operations unless they have untreated hyperthyroidism or severe hypothyroidism. Patients with known primary or secondary adrenal insufficiency require supplemental glucocorticoids to prevent adrenal crisis in the perioperative setting. Evidence supporting the use of high-dose supplemental corticosteroids for patients undergoing long-term glucocorticoid therapy is sparse. We discuss an approach to these patients based on the dose and duration of ongoing or recent corticosteroid therapy. As with other components of the preoperative medical evaluation, the primary objective is identification and assessment of the severity of endocrine issues before surgery so that the surgeons, anesthesiologists, and internal medicine professionals can optimize management accordingly.Copyright © 2020 Mayo Foundation for Medical Education and Research. Published by Elsevier Inc. All rights reserved.