Established in 1964, the Journal of Peace Research (JPR) celebrates 50 years. This anniversary special issue of the journal offers broad reviews of research areas that have been central both to the journal and to the field of peace and conflict research generally. An opening article co-authored by long-time editor Nils Petter Gleditsch offers a historical view on peace research and tracks trends in the use of ‘peace’ and ‘violence’ in titles of JPR across the first 49 volumes of the journal. Opening the review article section, two contributions address key thematic areas for the journal. Few if any subjects have attracted more attention in the study of international relations during the second half of JPR’s first 50 years than the democratic peace, and in the extension of this subject, the broader debate about the liberal peace. Additional articles review the status and propose future developments in the study of war and its relationship with territory, ethnicity, ideology and natural resources. Another key historical topic associated with the journal concerns the economic cost of military conflict, while more recent research fields covered include terrorism and human rights, topics that have grown to become major JPR niches. Reflecting the methodological contributions by JPR, two articles focus on challenges of contemporary quantitative political analysis and progress in peace and conflict data collection. Finally, this special issue includes a review of research on international mediation in armed conflicts.