Chapter Abstract: This chapter explores the third phase of development in Calvin’s doctrine of baptismal efficacy by examining six major works from the early years of his second ministry period in Geneva (1541–48): the Catechism of the Church of Geneva (1542/1545), the baptismal liturgy in The Form of Prayers (1542), the second revision of the Institutes (1543), his commentary on 1 Corinthians (1546), a polemical treatise, Acts of the Council of Trent: With the Antidote (1547), and his commentaries on Paul’s epistles to the Galatians, Ephesians, Philippians, and Colossians (1548). The evidence adduced in this chapter shows that although Calvin did not move in a substantially new direction in his understanding of the efficacy of baptism during this period, he did shift to an entirely positive use of the term “instrument” and to a heavier emphasis on baptism as a means of grace.