The clinical decision to treat early-stage breast cancer with adjuvant chemotherapy is sometimes a difficult one because 70-80% of patients who receive chemotherapy would probably have survived without it. To help clinicians in this decision-making process, different tools or 'decision aids' have been developed for the treatment of early breast cancer over the years. Some of these tools include clinical treatment guidelines and computer-based programs as well as different prognostic and/or predictive tests such as those based on gene expression profiles or the presence minimum invasive disease. All of these tools try to individualize as much as possible the estimation of the risk of breast cancer relapse and death and to facilitate the clinical decision about giving additional treatment, and ultimately the most appropriate treatment to be given. Thus, it is important for clinicians to be aware of not only the existence of these tools or 'decision aids', but also to know how they have been developed, how frequently there are revised and if they have been validated. In order to address all these concerns, we have carried out a critical review of the most important prognostic tests and clinical guidelines for the treatment of early breast cancer. Information regarding their development process as well as frequency of revision, validations that have been performed and main limitations of each tool were gathered and critically analyzed.