Although democracies in the past have participated frequently in interstate war, stable democracies hardly ever fight one another and they rarely suffer civil war or other serious domestic violence. The current wave of democratization therefore holds real promise for a more peaceful world. In this project, researchers from the Centre for the Study of Civil War at PRIO, the Department of Peace and Conflict Research at Uppsala University, Helsinki University, and Copenhagen University have collaborated on generating new and improved data to measure democracy (Tatu Vanhanen’s Polyarchy measure). They have also studied what forms of democracy are best suited for the promotion of internal and external peace. Finally, some recent papers from the project take a pessimistic view of the possibility of promoting democracy by outside force.