In a retrospective study on 59 patients (2 hypothalamic, 44 pituitary, 13 no confirmed disease) 69 pairs of insulin hypoglycemia tests (IHT) and short metyrapone tests (SMT) were evaluated. Cortisol and 11-desoxy-cortisol rsp. were compared as the endpoints. In 6 cases, the IHT was a technical failure because of insufficient hypoglycemia. In 25% of 63 pairs of tests, both tests were normal, (Group I), in 30% both abnormal (Gr. II). In 21%, IHT was normal, SMT abnormal (Gr. III) and in 24% IHT was abnormal and SMT normal (Gr. IV). The 2 patients with hypothalamic disease were in Group IV with completely normal SMT and severely pathological IHT. Other discrepancies could not be attributed to special pituitary disorders. In 9 patients of Group III and in 8 patients of Group IV (n = 17), the IHT alone was repeated 6-48 months after the original pair of tests which had been performed in most cases early after pituitary surgery. In 12 cases, the repeat IHT followed the trend of the SMT of the original test pair. In 5 cases, the IHT was unchanged. 14 of 19 patients of Group II, but only 5 of 28 patients of Group III and IV required permanent substitution with hydrocortisone.