The purpose of this study was to assess the potential prognostic and/or predictive value of the expression of cyclin D1, cyclin E, and p21 protein in a series of 98 anal carcinomas (T1-4, N0-3) treated by radiotherapy with (51) or without (47) chemotherapy in one institution. Correlation with Mib1 index and p53 expression was also investigated. Median follow-up for surviving patients was 124 months (range: 30-266). Immunohistochemical staining was performed on pretreatment biopsies, applying a standard ABC technique for cyclin D1 (clone DSC6, DAKO, 1 : 300), cyclin E (clone 13A3, Novocastra, 1 : 100), p21(WAF/CIP1) (clone SX118, DAKO, 1 : 50), p53 (clone DO7, DAKO, 1 : 200), and Mib1 (Ki-67, Dianova, 1 : 20). Tumours were classified into low- or high-expression groups according to the expression level of the protein considered. High expression was found in 51% of tumours for cyclin E, in 33.7% for cyclin D1, and in 65% for p21. None of those factors were significantly associated with clinical variables such as advanced T or N categories. In a monovariate analysis, advanced T and N categories and longer overall treatment time were the only variables that correlated significantly with low rate of local control (LC) and disease-free survival. However, in a subgroup analysis, high p21 expression correlated with a trend for significantly higher 5-year LC (87 vs 68%, P=0.07) in the N0 patients. The results of this study suggest that the cell-cycle proteins investigated are unlikely to be clinically useful in predicting treatment response or prognosis in patients with anal carcinomas.