The p53 gene is located on the short arm of chromosome 17. It encodes a 53-kd nuclear protein (p53) found in scant amounts in normal tissue. Mutations of the p53 gene have been reported in different human tumours. In breast cancer, it has been noted that the overexpression of p53 protein in the nucleus is an indicator of poor prognosis, although there is a high degree of variability, which may be due to different immunohistochemical techniques, varying assessment of results and the type of monoclonal antibody used. This study is an immunohistochemical analysis of p53 expression in 192 cases of infiltrating ductal carcinoma of the breast, correlating it with clinicopathological factors and the clinical course of the disease. Of all the breast-cancer tissue analysed, stains for p53 antibody were found in 87 tumours (45.3%). The results of multivariate analysis show that the independent predictors related to recurrence are tumour size, lymph-node metastasis and p53, while those related to death are necrosis, lymph-node metastasis and p53. In summary, our series showed prognostic significance between the expression of p53 and shorter survival time and disease-free interval for all patients in general as well as those who presented lymph-node metastases at the time of diagnosis.