This study provides a much-needed historical overview of the main developments in the theory and practice of Christian mission in this century. Part 1 describes the great missionary conferences of Edinburgh 1910, Jerusalem 1928, and Tambaram, Madras 1938, with particular emphasis on Christian responses to Hindu, Muslim, Buddhist and secular interpretations of religious life. In Part 2, the developing pluralism of the modern world is addressed by way of Roman Catholic, Orthodox, and evangelical documents, and through diverse contemporaneous thinkers.