The potential efficacy of early repeat transsphenoidal surgery for persistent Cushing's disease has not previously been examined. On 222 patients with no prior pituitary treatment and a preoperative diagnosis of Cushing's disease, 29 (13%) remained hypercortisolemic after an initial transsphenoidal pituitary exploration. Seventeen of these 29 patients underwent further surgery 7 to 46 days after the initial transsphenoidal approach in order to completely excise suspected residual tumor. Patients were followed for 4 to 84 months (mean +/- standard deviation, 34 +/- 25 months) to document sustained remission or recurrence of Cushing's disease (a urine free cortisol level > 90 micrograms/day was considered evidence of recurrence). Of the 17 patients with repeat surgery, 12 (71%) had resolution of hypercortisolism (morning plasma cortisol level < 5 micrograms/dl); however, in three of these 12, hypercortisolism recurred 5, 12, and 24 months later. In 14 patients a lesion that appeared to be a tumor was identified during the initial procedure or on histological examination. Of these, 12 had immediate resolution of hypercortisolism and nine are still in remission. Three patients, in whom no adenoma could be identified during the initial surgery or an examination of the partial hypophysectomy specimen from the initial surgery, had persistent Cushing's syndrome after the second operation. Seven (41%) of the 17 patients developed hypopituitarism requiring treatment with thyroid hormone, gonadal steroid, or vasopressin replacement. The low incidence of identification of an adenoma on computerized tomography or magnetic resonance images (three of 17 patients), the failure to find a corticotrophic adenoma during the initial surgery (10 of 17 patients), and the failure of these 17 patients to respond to the initial transsphenoidal surgery suggest that they may comprise a subset of patients who are more difficult to treat successfully with surgery than most patients with Cushing's disease. Despite that, early reoperation induced immediate remission of hypercortisolism in 71% of cases, but did so at the expense of a high risk of hypopituitarism. However, since the alternative treatments (such as radiation therapy, long-term drug therapy, or bilateral adrenalectomy) also have potential adverse effects, early reoperation deserves consideration for the management of persistent Cushing's disease, especially when an adrenocorticotrophic hormone-secreting adenoma was partially excised during the first surgery.