Objective In the last decade, pre-operative medical cortisol suppression therapy has frequently been used in Cushing's disease to normalize cortisol concentrations pre-operatively. Our aim was to assess the efficacy of presurgical medical cortisol suppression therapy in Cushing's disease. Design and Methods We retrospectively assessed the medical files of all patients with Cushing's disease that received presurgical cortisol suppression therapy with ketoconazole or metyrapone and underwent subsequent transsphenoidal surgery between 1990 and 2010 at our centre. We retrieved the pretreatment regimen, adequacy of pretreatment, early postoperative serum cortisol levels, adverse effects and long-term remission status. Results Nineteen of 33 patients (58%) obtained long-term remission after pituitary surgery without additional postoperative therapy. Thirteen of 16 patients with adequate presurgical cortisol suppression therapy had postoperative cortisol concentrations <50 nmol/l. The 16 patients with adequate presurgical cortisol suppression had a higher long-term remission rate after primary surgery compared with the 13 patients with borderline or inadequate pretreatment (81% vs 38%; P < 0·05). Conclusions Adequate presurgical cortisol suppression treatment with ketoconazole or metyrapone in Cushing's disease seems to be associated with suppressed postoperative cortisol concentrations and an increased long-term remission rate.