Aggressive pituitary corticotroph tumors causing Cushing's disease are rare, and there is limited data about their clinical management. Here, we aimed to report our long-term experience with gamma knife radiosurgery (GKRS) as adjuvant treatment in patients with residual or recurrent pituitary corticotroph tumors. This retrospective study included 45 adult patients (M/F, 7/38; mean age, 40.2 +/- 13.1 years) with residual tumor or recurrence after initially successful surgical resection. Single-session GKRS was performed in all patients. Tumors with a Ki-67 value higher than 3 % and radiologic invasion to surrounding tissues were classified as aggressive tumor group. Clinical, hormonal and radiological findings were compared between the aggressive (n = 10) and non-aggressive adenoma (n = 35) groups. Following GKRS, tumor volumes were significantly reduced in both groups. The mean time to hormonal remission in the non-aggressive group was significantly shorter than in the aggressive group (23.5 +/- 6.3 vs 33.0 +/- 5.0 month, respectively, p < 0.05). New-onset hypopituitarism was identified in only seven patients (15 %) after GKRS in the whole cohort. The present study introduces several essential findings about aggressive corticotroph tumors. First, aggressive behavior tends to occur more frequently in male subjects. Second, time to GKRS was significantly shorter in the aggressive group. Moreover, a tumor volume >= 2 cm(3) may be associated with clinical aggressiveness in corticotroph tumors. In conclusion, we suggest that early adjuvant GKRS is an effective treatment option in aggressive pituitary corticotroph tumors.