Since the inception of the RE conference series (1992), both researchers and practitioners in the RE com-munity have acknowledged the significance of empirical evaluation as an instrument to gain knowledgeabout various aspects of RE phenomena and the validity of our research results. A significant number ofempirical studies have been conducted in the search for knowledge about RE problems as well as evidenceof successful and less successful application of proposed solutions. This editorial presents the progressempirical RE research has made since 1992. Based on a search in the Scopus digital library, we reportfrom an analysis of peer-reviewed systematic literature reviews and mapping studies to showcase majorareas of RE research that use methods from the Empirical Software Engineering paradigm. We summarizeprior empirical research in RE and introduce the contributors to this special issue on empirical researchmethodologies and studies in RE.