Judith Becker's dissertation (University of Bochum) rightly won two significant German prizes on its way to being published in Brill's Studies in Medieval and Reformation Traditions. This thorough and persuasive monograph examines John à Lasco's ecclesiology as elucidated in his writings and then carefully traces the practical implementation of this theology in three congregations heavily influenced by him. Fully attentive to the surge in research in recent decades on Emden, Lasco, church discipline and the foreign refugee communities, Becker's study is well placed to provide a comprehensive analysis of the interplay of doctrine and practice in the experiences and aftermath of this important reformer. Lasco's church ordinance for the London foreign congregations, Forma ac ratio tota ecclesiastici ministerii (composed 1550, published 1555), usually provides the concrete foundation for analysis of Lasco's ecclesiology. Becker's examination, too, begins with this document, but she quickly broadens her careful theological analysis to contextualise it within Lasco's experiences in the congregations and in light of his other writings. Becker describes Lasco's Forma ac ratio as being part apology, part advertisement and part instruction, and with this three-fold purpose she indicates its usefulness both within and beyond the London congregation: by reflecting the development of the London congregation, his published church ordinances demonstrated that Lasco's ideal congregational vision could in fact be realised. Lasco's position as Superintendent of the East Frisian churches before overseeing London's Dutch and French-speaking foreign Protestant congregations provide the opportunity to gauge the influence of his prior experiences and to trace the relationships between Lasco's formal writings and the subsequent developments within these congregations. Becker accomplishes this by looking at the Forma ac ratio in light of Lasco's collaboration and indirect connections with other Reformed writers before moving on to reconstruct the practical congregational experiences. Approximately three-quarters of Becker's monograph is devoted to a detailed dissection of the internal structures during the second half of the sixteenth century of the three congregations with the closest ties to Lasco's leadership, namely that in Emden and the two foreign Protestant congregations in London (following their re-establishment early in Queen Elizabeth's reign). Sensibly organised to allow as much cross-comparison as possible, these three long chapters reveal the ways in which each congregation defined its church offices and various kinds of congregational membership (and exclusion) and implemented church discipline. By buttressing her analysis with a thorough reading of each congregation's surviving church council records, Becker's reconstructions of their practical functioning offer fresh insights into the activities, work and even self-conception of the congregational officeholders. Disputes and conflicts provide opportunities for Becker to measure the boundaries of congregational definition and church discipline. Her finale to this well-written book gives us general conclusions about the standardisation of certain Reformed norms in ecclesiology and church discipline that developed out of congregational and synodal experiences as well as various doctrinal texts and church ordinances during the second half of the century. Becker has produced an eminently satisfying and compelling monograph which, with great insight, analyses the relationship between doctrine and practice.