The development and implementation of evidence-based, interdisciplinary, consensus-based guidelines is a very important step towards decreasing breast cancer mortality and optimizing the process of early detection, diagnosis, therapy, and follow-up of breast cancer. A revised version of the German S3 guideline was published in February 2008. Different working groups, departments, and organizations participate as coeditors of the new guideline. To fulfill international methodic requirements, a systematic search of the literature with selection of new publications (used as evidence) in the established data bases (Medline, BIOSIS, Previews, CDSR, ACP Journal Club, DARE, CCTR, CINHAL) and the Guidelines International Network (GIN) was performed for the time period of 2003–2006. Varied specialist opinions concerning diagnosis, therapy, and follow-up of breast cancer were considered in formal consensus processes. In different steps, Nominal Group Process techniques, the Delphi technique, and formal consensus processes were used. Besides differently weighted, study-based recommendations, statements resulting from structured consensus finding by the interdisciplinary group – in terms of good clinical practice – were postulated.