The A. shows how three renowned theologians belonging to different Christian denominations both meet and differ in their approach of an «ecclesiology of communion». All three share a common trinitarian insistence. Roman Catholic Y. Congar centres his thoughts around the «divine missions»; Orthodox J: Zizioulas, around the «trinitarian relationships»; Lutheran J. Moltman, around «God's sovereign presence in the course of history». These various stresses constitue a solid foundation for ecumenical dialogue. Each of these, theologians draws meaningful implications from his own viewpoint: concerning the «unity of communion» (Congar), the «Eucharistic communion» (Zizioulas), the. «unity of community» (Moltmann). All three emphasize the eschatological dimension of ecclesial communion.