In very premature infants of less than 30 weeks gestational age there is no correlation between the severity of illness and plasma cortisol concentrations. Low plasma cortisol levels were measured during critical illness with severe arterial hypotension requiring catecholamine treatment in the first two weeks of life. Thus, a relative adrenal insufficiency is suspected. The pituitary responds to CRH and the adrenal cortex to ACTH. But it is still questionable, wether the response is sufficient. Preterm infants with an impaired adrenal function in the first weeks of life seem to be at a higher risk for developing bronchopulmonary dysplasia. Steroids are effective in the treatment of arterial hypotension and bronchopulmonary dysplasia. Because of the broad spectrum of severe and long-term adverse effects, the treatment with glucocorticoids is recommended only after carefully balancing its benefits and risks.