We report a case of a 64-year-old man with secondary adrenocortical insufficiency who has been on a chronic transdermal fentanyl treatment because of sciatic pain syndrome. Shortly before admission to our hospital, the patient had discontinued his hydrocortisone medication. Adrenal crisis was assumed and during therapy with hydrocortisone infusion, the patient recovered. We suspected an opiate-induced suppression of the hypothalamus-pituitary-adrenal (HPA) axis. Therefore, we gradually reduced the opiate dosage. After 1 week, HPA axis function was markedly improved. We conclude that opiate medication may inhibit - in a life-threatening way - the organism's ability to respond to physical, emotional or metabolic stressors.