We report the case of a 70 year old man who presented with physical and biochemical features suggestive of Addison's disease, but had a normal short tetracosactrin (Synacthen) test. Six months later he re-presented with similar clinical features but with an abnormal response to tetracosactrin confirming the diagnosis of Addison's disease. We recommend that if adrenal insufficiency is strongly suggested further investigation should be performed to exclude this diagnosis.