The TP53 protein is proving to be central to cell cycle control after exposure to DNA damage, and every week a new feature of its role in the regulation of cell division is described. TP53 is the most commonly altered oncogene in human tumours and is involved in the development of both sporadic and some hereditary breast tumours. Although there is no doubt that germline mutations in the TP53 gene carry a high risk of early onset breast cancer, and the gene is mutated somatically in a proportion of preinvasive and invasive breast cancers, it is not usually the initiating genetic event in most breast tumours. It does, however, seem to be an independent prognostic factor for survival and could prove useful in clinical management of node negative breast cancer patients. There has been an explosion of reports about the function of the TP53 protein--in particular, it seems to have a central role in the monitoring of some types of DNA damage. This role may prove to be the most important aspect of its association with breast cancer development, both as a prognostic factor and as a handle for treatment.