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The clinical management of invasive breast cancer has changed during the last decade with the use of molecular-based multigene assays (MGAs).They are increasingly used to gain additional prognostic and predictive information and guide adjuvant treatment decisions. Since 2004, several MGAs have become available but, four of them are the most widely used in clinical practice: the OncotypeDX^® Breast Recurrence Score, the 70-gene signature MammaPrint^®, the Prosigna^® (PAM50) and the EndoPredict^® (EP/EPclin Scores) assay. However, MGAs are not all the same and they do not provide interchangeable information. They differ in terms of the technological platform used for their development, the number and specific genes assessed, and the patient populations in which they were validated. Furthermore, although they are all validated for providing prognostic information, not all of them are supported with data from prospective randomised trials confirming the clinical value of their use in chemotherapy treatment decisions in certain groups of breast cancer patients; in this regard, so far there are published data only for OncotypeDX and MammaPrint, whilst PAM-50 (Prosigna) and EndoPredict assays are currently not supported by entirely prospective randomized trials evaluating their predictive value of chemotherapy benefit. As such, inclusion of these MGAs in major international treatment guidelines differs in indications for their use in clinical practice as prognosticators only or as predictors of chemotherapy benefit as well. Use of MGAs in clinical decision making can lead to de-escalation of chemotherapy recommendations and thus save a large number of patients from unnecessary side effects and decrease the cost of breast cancer treatment to National Health systems. This review provides an overview of the four most widely used MGAs in clinical practice, including basic information on their development and validation, as well as recent data on the information they can provide.