Book excerpt: This historical dictionary covers the major trends in the 20th century ecumenical movement until today. It deals with developments in the realms of church unity, mission and evangelism, laity, women in church and society, and many other ecumenical subjects. It also covers many programs and activities of the World Council of Churches since its inception in 1948. The longer articles survey important theological themes while short articles provide quick reference on a precise question. The bibliography is not exhaustive-some 50,000 titles have been published since the beginning of this century-but very helpful for major bibliographical information. The dictionary is particularly strong in American subjects and includes a great number of ecuminical personalities which cannot be found in other reference works. This publication is not only an indispensible tool of research for university and seminary libraries but also for individual persons belonging to whatever Christian church who are interested in knowing more about reflections, relations, and activities in the several regions of the ecumenical world. A helpful description of the most important ecumenical assemblies and conferences is provided. To take stock of the past, to interpret the present, and to look forward into the third millenium of Christian existence are exciting and challenging enterprises.