Church communion - communio has become a key concept in ecclesiological deliberations in ecumenical contexts. This volume presents the result of a doctrinal conversation, adopted by the General Assembly of the CPCE in 2018, evaluating the church communion realised on the basis of the Leuenberg Agreement since its signing in 1973 and specifying the theological concept of church communion in the light of the latest ecumenical discussions. In addition, it contemplates the challenges that the CPCE currently faces as a communion of churches in Europe and suggests potential approaches to further intensifying this communion. This volume also contains a reprint of a previously scarcely available text revealing key considerations prior to the conclusion of the Leuenberg Agreement, which provides an invaluable tool for understanding this model of church fellowship.