Probably few modern readers would anticipate the extent of animosity and fear in the sixteenth and seventeenth centuries over how people should pray, as revealed in Giorgio Caravale's Forbidden prayer. This translation of his L'orazione proibita, has been revised for an English-language readership: lengthy Italian and Latin quotations from recondite literature and Holy Office records remain, but are fully translated. The concerns were varied, and considered both personal praying and prayers in the liturgy; how efficacious was praying in incomprehensible Latin; was vocal prayer largely sterile (as Savonarola argued), and were there dangers in the Pater Noster (leading to Lutheranism according to Alvise Lippomano in 1547); was the use of the vernacular a pathway for new Lutheran ideas (as Nunzio Girolamo Aleandro in Venice alleged in 1532: p.72 n. 5)? How could authorities curb the use of popular prayers for superstitious purposes, without undermining enthusiasm for traditional prayers that were less harmful? To what extent was silent mental prayer, speaking to God, seeking ‘sweetness and gentleness’ (p. 29) in mental union with God (as Cardinal Federico Fregoso wrote), acceptable? Or did this lead to unacceptable mysticism, to ‘spiritual nuptials’ with men feeling ‘inflamed with heavenly fire’ (as Lorenzo Davidico suggested: p. 54 n. 56), so encouraging retreat from the real world and from good works, and removing lay people from clerical direction? While the battles of the inquisition against mysticism, Quietism, Molinism and the Pelagini are fairly well known through recent work by Gianvittorio Signorotto, Marilena Modica or Ignacio Tellechia Idigoras, here in the early chapters Giorgio Caravale illumines the precursors in the sixteenth century, such as Davidico (who just escaped serious punishment, though imprisoned), his master Battista da Crema and another pupil, Serafino da Fermo. Caravale then contributes significantly to understanding of the processes of censorship by the Congregations of the Holy Office and of the Index, especially using censors’ reports and letters surviving in the Archivio della Congregazione per la Dottrina della Fede. Throughout the later chapters, and in fascinating detail, Caravale indicates the practical problems of censorship as these competing Congregations and the popes followed different criteria, as they and local inquisitors battled to establish acceptable texts of prayers and Offices, seeking to banish false indulgence promises, and to remove prayers against storms, fever, plague or enemies, or prayers to set off women's labour. The long campaign for liturgical uniformity was lost, as recognised in the 1604 Missal. Variations based on past privileges and with a long tradition were tolerated if in private (including within confraternity services), but not in public, as Rome made clear to the Modena inquisitor in 1609 and 1614 (p. 242 n. 61). The 1601 papal decree on litanies symbolised another failure of an austere policy (and of the Index Congregation's control); older local differences had to be accepted, though ‘novelties’ should be weeded out. Ample quotation shows censors at work on books on public and private prayer, some astute, others too paranoid about possible ‘Lutheran’ influences. Worth noting is Giovanni Battista Porcelli, an astute inquisitor of Asti, strongly interested in orationi and historietti, and active applier of the 1596 Clementine Index, whose correspondence seemingly helped to rationalise Roman policies.