This essay discusses how Christian ecumenism and interreligious theology and dialogue may benefit from each other. Beginning with overviews of points of concurrence among world religions and typologies of Christian attitudes toward world religions, it explores the relevance to interreligious dialogue of key notions from ecumenical experience: the identification of appropriate dialogue partners, the importance of understanding the other, "purification of memory," ecumenical and interreligious "gift exchange," personal friendship, and common prayer. Some types of unity sought in Christian ecumenism are relevant in interreligious dialogue, while others are not. Particular obstacles in interreligious dialogue are less significant in ecumenism: interreligious violence, the politicization of religious identity, the "dilution" of religious beliefs, and risks of Christian relativism. Lessons relevant to interreligious understanding and dialogue are sought in the works of Fr. Lev Gillet and Christina Mangala Frost.