Markus Barth's book Die Taufe: Ein Sakrament? had an evident and important influence on the development of his father Karl Barth's theological understanding of the nature and practice of Christian baptism. This essay explores that influence, considers its scope and significance, and suggests in the course of so doing that the relationship between the elder and the younger Barth is a notable factor in what led to the provocative theology of baptism at which Karl Barth arrived in the late, fragmentary volume of the Church Dogmatics. Markus Barth's book Die Taufe: Ein Sakrament? had an evident and important influence on the development of his father Karl Barth's theological understanding of the nature and practice of Christian baptism. This essay explores that influence, considers its scope and significance, and suggests in the course of so doing that the relationship between the elder and the younger Barth is a notable factor in what led to the provocative theology of baptism at which Karl Barth arrived in the late, fragmentary volume of the Church Dogmatics.