The ecological crisis was a complex social phenomenon which caused some concern and public debate in the Western industrialised nations in the late sixties and early seventies. The crisis situation has been discussed in the World Council of Churches, which formulated its goal in social ethics in terms of the Just, Participatory, and Sustainable Society. Most of the ecumenical discussions about the sustainable society have taken place in the programme of the Church and Society subunit, which has been concerned with the place of technology in such a society. It held a major conference at the Massachusetts institute of Technology in 1979, on 'The Contribution of Faith, Science and Technology to the struggle for the Just and participatory and Sustainable Society' , and it had already conducted an intense investigation from 1969 to 1974, on 'The Future of Man and Society in a World of Science-Based Technology'. The basic problem seems to lie in ethics rather than systematic theology; but I argue in Chapter One that the ecological crisis involves questions at the level of systematic theology. My Chapter Two is concerned with making precise the concept of an 'ecological theology' within theological discourse and adducing as examples ecological theologies from a Barthian theologian, a process theologian, and a biblical theologian. Chapter Three analyses the ecumenical materials, and places the MIT conference in the ethical and theological history of the Church and Society programme. Four main theological approaches are found in the sources: an approach which sees nature as an entangling force from which humanity is to emancipate itself by scientific and technological skill; a theology of hope; a process theology; and an Orthodox approach. These are described, analysed, and evaluated in Chapter Four, and the orientation they give for Christian life in the technological culture is described. The conclusions of this thesis include some constructive criticisms aimed at assisting the Church and Society programme and enhancing its theological adequacy.