Adrenal insufficiency (AI) is a rare disease in childhood and adolescence that results from disruption in the hypothalamic-pituitary-adrenal axis. Pediatricians should be familiar with this entity since acute adrenal crisis is a life-threatening condition that requires immediate treatment. In the early stages of AI, the clinical manifestations may be subtle and non-specific; thus, they are frequently unrecognized. The main therapeutic approach in all forms of adrenal insufficiency is glucocorticoid replacement; the dose should be titrated appropriately to avoid under or overtreatment. Patient and family education is particularly important, to enable adjustment of dosage replacement therapy during stress and to prevent crisis. This article summarizes the current knowledge of AI and provides new insights on its management in children.