PURPOSE: To evaluate the prognostic factors for disease-free survival and long-term results of radiotherapy for pituitary adenoma. METHODS AND MATERIALS: The study involved a retrospective review of outcome in a series of 27 patients with pituitary adenoma, between 1984 and 1995 at Paik hospital. The study included 20 patients treated with surgery and postoperative radiotherapy and 7 with radiotherapy alone. The patients were followed for 12-146 months (median : 97 months). Seventeen were men and 10 were women. The numbers of functioning and non-functioning pituitary adenoma were 22 and 5 respectively and those of microadenoma and macroadenoma were 4 and 23 respectively. The radiation doses of 5040-5580cGy (median : 5040cGy) were deliverd over 5-7 weeks, using 4MV LINAC. The prognostic factors were analyzed by log-rank test. RESULTS: For radiation therapy alone, the 5YSR was 100% and progression free survival rate was 85.8%. The tumor was controlled in 6/7 (85.8%). For surgery and postoperative radiotherapy, the 5YSR, progression free survival rate and local control rate were 95%, 84.8%, and 89.5% respectively. The parameters of tumor size, hormone secretion, radiation dose, radiotherapy field size were evaluated in a uni- and multivariate analysis and all the factors were not statistically significant (P > 0.05). Eleven of 12 (92%) with visual field defect experienced normalization or improvement, and 5 for 7 evaluable patients with hyperprolactinoma achived normalization in 4 and decrement in 5 patients. Only 2 patients developed mild degree of panhypopituitarism. CONCLUSION: The radiotherapy appears to be effective in controlling clinical symptoms and signs resulting from pituitary adenoma. Local control rate with radiotherapy alone or with surgery and postoperative radiotherapy was comparable. There was a trend toward high recurrence rate in patients with nonfunctioning or prolactin secreting tumor and larger radiation field sizes.