BACKGROUND: Gamma-knife is characterized by low risk and low death rate, without trauma, bleeding or infection. MRI has replaced CT as a method of location, and provides a good choice for treating pituitary tumors.OBJECTIVE: To analyze the effectiveness and complications of 501 cases with pituitary adenoma by using gamma-knife retrospectively.DESIGN: Case-analysis.SETTING: Gamma-knife Center, the 363 Hospital of Chinese PLA.PARTICIPANTS: A total of 501 cases were selected from Gamma-knife Center, the 363 Hospital of Chinese PLA from January 1997 to December 2002. All patients were certainly diagnosed with CT and MRI scanning. There were 186 males and 315 females. Their ages ranged from 15 to 84 years with the mean age of 39 years. All patients provided confirmed consent.METHODS: All 501 cases with pituitary adenomas were treated by gamma-knife or combined with operations: The average iso-dose curve was 50% (30% - 65%), peri-dose was 14 Gy and the average target number was 5.17. ① At 35 months after treatment, patients received follow-up including clinical symptoms,imaging symptoms and endocrine symptoms. ② Patients who received second gamma-knife treatment were analyzed and their complications were observed after operation.MAIN OUTCOME MEASURES: ① Follow-up results of clinical symptoms, image and endocrine indexes; ② second gamma-knife treatment; ③ postoperative complications.RESULTS: Among 501 accepted patients, 275 cases were involved in the follow up of clinical symptoms,154 in image symptoms and 98 in endocrine symptoms. ① Follow-up results of clinical symptoms, image and endocrine indexes: Follow up of clinical symptoms demonstrated that clinical symptoms of 169 cases were relieved, of 68 disappeared, and of 38 deteriorated. Follow-up of image symptoms indicated that pituitary tumor of 25 cases disappeared, of 84 shortened, of 42 not changed, and of 3 enlarged. Follow-up of endocrine symptoms suggested that endocrine of 50 cases was abnormal, of 29 recovery to normal value, and of 19 not changed obviously. ② Second gamma-knife treatment: At 6- 24 months after gamma-knife treatment, 15 patients with pituitary tumor received second gamma-knife treatment; especially, one patient received for the three times. The conditions in details were recorded as follows: The peri-dose for the first treatment ranged from 8 to 12 Gy; in addition, that for the second one ranged from 6 to 12 Gy. ③ Postoperative complications: The complications were as follow: hypopituitarism occurred in 2 patients (0.7%); tumor apoplexy in 2 patients (0.7%);weakened eyesight in 5 patients (1.8%); 3 of which recovered with dehydration and hormone treatment; 2 patients received tumor resection and optical nerve decompression operation with dehydration and hormone treatment ineffectively.CONCLUSION: Gamma-knife is effective and safe for pituitary adenoma.