In 20 patients we studied the function of the corticotropic pituitary and adrenal gland 13 to 45 month (m = 27.1) after heart transplantation (HTx). For prophylactic immunosuppression all patients were treated with triple drug therapy, including Cyclosporine A, Azathioprine and Prednisolone. After performing the CRH-test we could demonstrate, that in all patients, treated with Prednisolone (0.09-0.15 mg/kg/day) for more than 1 year, adrenal insufficiency was evident. Patients must be controlled carefully, if therapy with steroids is stopped thereafter, not only because of increased risk of rejection but also because metabolic disturbance caused by adrenal insufficiency may occur. In case of elevated demand of steroids (i.e. infections or surgery), adequate substitution with glucocorticosteroids is needed.