In the foreword to this volume the editor admits immediately his debt to H. Polack for a usable text and to the work on the manuscript tradition by H. Hörner, albeit with considerable reworking. At the same time he has gone directly to photographs of manuscripts collected in Harvard by W. Jaeger in around seventy-five cases, and for the conspectus of the codices he has been helped by the Institut für byzantinische Rechtsquellen. This is truly a team effort. Then follows the conspectus – a listing of all the manuscripts available. The introduction to the work itself occupies the lion's share (107 pages) of this slim volume. Non-specialists might be surprised to learn that this is the most transmitted piece by Gregory, owing to the fact that it got taken up with the Byzantine canonical-legal collections. The text of the epistle in P.-P. Joannou's 1963 edition of this collection left a lot to be desired. The conclusion seems to be that textual variation has more to do with copyist errors than to diverse early source traditions. We next learn about the relationship of the earliest canonical collections: the Synagoga L titulorum, the Nomocanon XIV and the Syntagma XIV titulorum. Each of these three is paid scrupulous attention with respect to variants within them. There does not seem to be much evidence in favour of a collection of patristic letters pre-existing the sixth century. This reviewer found the further exploration of codices families technical to the point of being harder to follow. It appears that Gregory's letter was then apparently excised and re-edited, perhaps intentionally, by the tenth-century monk Arsenius. The text as found in Balsamon's commentary and the Syriac translations (rather late and reflecting a divergent Vorlage) are also given some separate treatment, before the printed editions of Paris 1615 and 1638 are discussed, along with a discussion of Pitra's 1864 distaste for Photius' Nomokanon on the grounds that it made secular and canon law to be of equivalent authority. It would perhaps be churlish to expect any amount of discussion of the content of the text. The Gregorii Nysseni Opera series attempts to be more consistent in this respect than, say, the practice of the CCL. And yet one wonders whether one can really treat the history of transmission and redaction totally apart from questions of content. Or at least the reader could be alerted to that content. To take one example from the text: Gregory sets the scene by talking about the feast but the single reference in the margin to Psalm cxi.5.6 on the grounds that there is sufficient closeness to the LXX text shows a lack of awareness of how Gregory used Scripture to draw in multiple sources by allusion.