In last years an increasing number of evidences has been gained that inflammatory response plays a major role in critical illness. The acronym SIRS (Systemic Inflammatory Response Syndrome) has been introduced to define the condition in which the inflammatory reaction exceeds local mechanisms of containment and inflammatory mediators invade the bloodstream causing systemic disturbances. Theoretically, the use of corticosteroids offers a potent tool to control the excess of inflammatory reaction, but initial trials on Adult Respiratory Distress Syndrome (ARDS), head trauma, and septic shock showed not only that mortality was unaffected, but also that morbidity could increase. Recently, however, some new studies have suggested that corticosteroids given at dosages lower than those initially tested, could positively affect late stages of ARDS by preventing pulmonary fibrosis, and septic shock by improving hemodynamics and facilitating the weaning from catecholamines. To date, it is not clear whether these effects are related to the correction of an adrenocortical dysfunction.