Written in 1159, the full text of Policraticus survives in over 60 manuscripts. This new critical edition is the first to examine all the surviving twelfth and thirteenth century manuscripts, as well as some later ones. The text is based on 11 manuscripts, ranging in date from c. 1160 to 1406. The detailed examination of the manuscripts and the manuscript tradition in the Introduction isolates two authorial versions of the text. Both versions were recorded in London BL Royal 13 D IV, the earliest and most authoritative of the extants manuscripts. This manuscript was used by the last editor, C.C.J. Webb, for his 1909 edition, but his preference for MS Corpus Christi College, Cambridge 48 meant that in effect he printed the earlier version of the text. The evidence of Royal 13 D IV suggests that Salisbury revised the text to produce his second version before he went into exile in 1166. The evidence of two later manuscripts indicates that a major revision of the text, constituting a non-authorial third version, originated in Italian jurist circles in the mid-fourteenth century. The manuscript tradition bears comparison with that of Salisbury's other major work, Metalogicon (the subject of a recent exhaustive study by Dr Keats-Rohan), which has been revealed as the key to Policraticus by P. von Moos and others. The readings of the four previous editions have been added to those of the MSS in the apparatus criticus, in order to produce a full account of the textual transmission of the work. The new edition adopts C.C.J. Webb's acclaimed apparatus fontium in extenso, though the opportunity has been taken to revise and to augment it, based on the publications of recent years as well as archive work. In addition, quite apart from reference to John's sources, Webb's app. font. contains much information about the way that Policraticus was used by later writers. Languages: Latin.