We have performed univariate and multivariate analysis to identify the clinical and treatment-related prognostic factors in a series of 254 patients with newly diagnosed, histologically proven, oropharyngeal squamous cell carcinoma treated with radical radiation therapy. The probabilities of local control, regional control, disease-free survival (DFS) and adjusted survival (AS) were calculated using the Kaplan-Meier method and differences between curves were evaluated by the Mantel-Cox test. The obtained significant variables in the univariate analysis were analysed using the Cox proportional hazards model. In the Cox multivariate analysis, four variables significantly influenced local control probability in the following order: tumour diameter, N stage, alcohol intake and weight loss. N stage significantly influenced the probability of regional control. Five variables influenced both DFS and AS: N stage, tumour diameter, weight loss, alcohol intake and tumour origin within the posterior oropharyngeal wall.