Regular treatment of large vestibular schwannomas (VS) is surgical resection of the tumor with attempt of facial nerve preservation. In a very reduced number of tumors, microsurgery is not warranted mainly because of controlateral deafness or the risk of life-threatening open surgery. The purpose of this study was to analyze the results of Gamma Knife radiosurgery delivered for large VS. Between July 1992 and January 2002, we treated 50 patients harboring a large VS defined as a Koos grade IV tumor. Data and follow-up were available for 45 tumors involving 44 patients, including 12 neurofibromatosis type 2. Mean age at the time of treatment was 43,5 (range: 14-84), mean diameter of the tumor in the CPA was 18mm (range: 12-30) and the mean Volume was 4301 mm3 (range: 1340-11405). Gamma knife treatment was undertaken using on average 13.4 isocenters (range: 4-48) and 10.2 Gy at the tumor margin (range: 8-14). Median follow-up was 45.5 Months (from 24 to 108 Months). Tumor control was 69% (interval confidence: 52-83%) and 3 patients had to be operated because of continuous tumor growth. Statistical analysis showed that tumor Volume was correlated to Gamma Knife failure in a uni-and multivariate model (p=0.027). No brain stem complication was observed. No facial nerve deterioration was found and hearing preservation could be obtained at a useful level in 12 out of 20 patients (60%). These results suggest that in a highly selected subgroup of patients with large VS, radiosurgery can be an interesting alternative to open surgery, particularly if hearing preservation is required. Information should be given to the patients that the risk of failure is greater than for small and medium sized VS.