Over 6 years (1992-1998) 26 patients with brain stem cavernomas were treated using the Leksell gamma knife in Prague. 25 patients had a follow up of 6-66, median 24 months. Annual risk of bleeding before radiosurgery was 4%. After gamma knife treatment sudden impairment of neurodeficit reported as rebleeding was observed in 4 patients at 6-51 months, median 16.5 months, after radiosurgery. This represented a 6.8% risk of rebleeding after radiosurgery, which is not significantly different from the risk before radiosurgery. MRI or CT was performed in 24 patients 6-48, median 24, months after radiosurgery. There were no signs of rebleeding in any of the patients, nor any increase of the cavernoma. A decrease of cavernoma size was observed in 8 (33%) of patients. Temporary collateral edema after radiosurgery was detected in 5 (21%) of patients 3-12, median 11, months after radiosurgery. Neurodeficit was observed in 21 of 26 patients before radiosurgery. Improvement of the neurodeficit was detected in 9 (43%) of them 6-36, median 8, months after radiosurgery. Temporary morbidity caused by collateral edema or rebleeding occurred in 7 patients (28%) and permanent morbidity remained in 2 patients (8%). 2 patients died because of rebleeding 6 and 51 months after radiosurgery and the third patient for unrelated reason. Radiosurgery of the brain stem cavernomas was indicated when there was bleeding in the history or progressive neurodeficit and microsurgery was considered too risky. Leksell gamma knife radiosurgery of cavernomas has proved its low morbidity and zero mortality. In case of an insufficient effect of radiosurgery, or if the protective effect from rebleeding comes too late, morbidity and mortality can correspond to the natural course of the disease, as it was left without any treatment.