Abstract. Ultimately aiming at a more individualized therapeutic approach in epidermoid anal cancer, this study explored the prognostic and predictive impact of a set of tumour markers. From a population-based cohort of 276 patients with epidermoid anal cancer, treated according to prospective protocols, 215 pre-treatment biopsies were investigated using immunohistochemistry. The expression of p53, p21, Cyclin A and CD31 was measured semiquantitatively. The expression rate was classified as high when immunostaining was seen in >5% of the tumour cells for p53 and p21, >20% in Cyclin A and, above median vessel count for CD31. Marker expression was correlated to survival and treatment response. A high Cyclin A expression correlated significantly with improved overall (77% vs 59%, p=0.005) and tumour-specific (81% vs 64 %, p=0.009) survival at 5 years. Also, the locoregional failure rate was significantly lower in patients with a high Cyclin A expression (12% vs 24%, p<0.05). In a multivariate Cox analysis Cyclin A was an independent prognostic factor. A low p21 expression correlated with a reduced rate of locoregional failure (14% vs 27%, p<0.05) but no impact on survival was found. For p53 and CD31 no significant correlations were obtained. Cyclin A may be an indicator of radiosensitivity and a valuable prognostic marker in epidermoid anal cancer.