Background: Morbidity and mortality from breast cancer in Europe, as well as costs associated with the disease, remain high. Patients treated according to existing guidelines have better survival. The European Commission Initiative on Breast Cancer (ECIBC) aims to improve quality of care by developing evidence-based breast cancer guidelines and supporting their implementation via a quality assurance scheme for breast cancer services. The goal of this study is to give an overview on compliance with breast cancer guidelines in Europe. Methods: Studies assessing adherence to guidelines on breast cancer screening, diagnosis, treatment and follow-up were searched via Pubmed. Studies published between 1990 and 2016 were included. Results: In total, 127 studies (mainly observational, retrospective, prospective, and cross sectional) were analysed. The number of participants varied from 56 to 72 000—with studies based on cancer registry data typically including more than 10 000 patients. Overall, adherence to guidelines was variable. Regarding treatment, (e.g. chemotherapy) adherence ranged from 70% to 96% and was approximately 50% for follow-up. Additional or 'unnecessary' procedures were cited as the main causes of non-compliance to follow-up. On the other hand, adherence with respect to radiotherapy (e.g. compliance with technical guidelines) and some safety-related aspects (e.g. cardiac monitoring during adjuvant trastuzumab therapy and prophylaxis with colony-stimulating factors) was substantially lower. Elderly patients were treated less frequently according to existing guidelines. Professionals with less experience (i.e. < 8 years) complied better with guidelines. Use of computerised decision support systems (CDSS) and implementation of a multidisciplinary breast cancer pathway led to better compliance. Conclusions: In Europe, adherence to guidelines is variable. Implementation of guidelines can help decrease variability in clinical practice, and improve treatment effectiveness and patient safety. Fortunately, adherence can be monitored through the use of quality assurance schemes (e.g., the ECIBC). Incorporating a CDSS within the clinical workflow could reduce the workload of physicians and thus increase their compliance with guidelines. Legal entity responsible for the study: European Commission, Directorate General Joint Research Centre European Commission, Directorate General Joint Research Centre. Funding: None Disclosure: All authors have declared no conflicts of interest.