Background and Objectives : To investigate the prognostic factors and effectiveness of radiotherapy for oropharyngeal cancer. Material and Methods : Forty seven patients in oropharyngeal cancer treated with radiotherapy between November 1989 and October 2010. Conventional radiotherapy was performed until July 2007 and conformal radiotherapy was performed since August 2007. Median age of patients was 59. Thirty five patients were males. Nine patients had operation. Patients treated with postoperative radiotherapy were delivered median 60 Gy and patients treated with definitive radiotherapy were delivered median 66 Gy. Median follow-up periods were 51 months. Results : Two year and 5 year overall survival rate was 78.7% and 59.9%. Two year and 5-year locoregional recurrence free survival rate was 82.3% and 72.9%. In subgroup of definitive radiotherapy, at univariate analysis for overall survival, lower N stage(p=0.01), lower stage(p=0.05) and well and moderate differentiation(p=0.001) were statistically significant. At univariate analysis for locoregional recurrence free survival, lower T stage(p=0.02) and better differentiation(p=0.043) were statistically significant. Treatment failure occurred in 12 patients. Locoregional recurrence(8 patients) was main pattern of failure. Conclusion : When definitive radiotherapy compared with postoperative adjuvant radiotherapy, there was no significant difference. Further studies would be needed to compare definitive radiotherapy with postoperative radiotherapy. N stage, stage and differentiation could be the prognostic factors for overall survival and T stage and differentiation could be the prognostic factors for locoregional recurrence free survival in patients treated definitive radiotherapy.