Corticosteroids are the mainstay of treatment of all asthma severity levels in adults and children. With their widespread use comes a responsibility to monitor, understand, and balance their efficacy and safety. Systemic adverse effects such as adrenal suppression have been clearly associated with the use of oral corticosteroids and to a lesser degree with the use of inhaled corticosteroids (ICS). In clinical trials, adrenal suppression is more evident when ICS are used in long-term therapy and at higher doses. However, monitoring adrenal suppression during short-term therapy and at lower doses is still of value in order to ascertain the lower limit of an inhaled corticosteroid's safety profile. Significant adrenal suppression at conventional ICS doses appears to be rare in clinical practice. When evaluating the effect of ICS on the hypothalamo-pituitary-adrenal-axis (HPA-axis), one must consider sources of variability both within and among trials including test sensitivity, systemic bioavailability, degree of airway obstruction, and delivery devices. All of these factors have the potential to effect the level of adrenal suppression detected and must be considered when interpreting HPA-axis test results in research or practice. This review will discuss adrenal suppression found with common ICS.