This volume offers in convenient form new editions with German translations of three texts bearing on Byzantino-Islamic relations. Two of them are fairly well-known. At the behest of Romanos i Lekapenos, Arethas of Caesarea wrote c. 921 a response to the emir of Damascus' critique of Christian teaching and proclamation of the superiority of Islam. The learned bishop's style is quite plain and a marginal note in our sole manuscript witness remarks that this style was suitable ‘for the comprehension of the Saracens’. Besides ridiculing Mohammed and expounding the Trinity through well-worn patristic comparisons with the light and heat of the sun, Arethas cites current events such as the continuing revolt of the Karmatians against the Muslim authorities in refutation of the emir's claim to be ‘waging war as God's Beloved’ and to be ruling the world (p. 38, lines. 263–4). Arethas insists that the emir's readiness to kill soldiers and civilians alike is a transgression, citing the Book of Wisdom (i.13). He also claims that ‘your false-prophet Mohammed’ forbade it in the Koran. As Karl Förstel points out, there is no such ban in the Koran, but the Prophet's treaty with the Christians of Najran does contain this injunction (p. 37 n. 11). The other well-known text is the twenty-eighth chapter of Euthymios Zigabenos's Panoplia dogmatica, ‘Against the Saracens’. Euthymios himself stated that he was only ‘marshalling’ armaments against heresy, not devising new ones, and cites lengthy passages of his sources verbatim, drawing heavily on St John Damascene and Niketas of Byzantium. The text is of little theological value, but the inclusion of a polemical chapter on Islam in the Panoplia, which Alexios i Komnenos commissioned in the wake of the First Crusade, is noteworthy. Of greatest import is the third text in this volume, a collection of the fragments of the Koran in Greek translation, garnered mainly from Niketas, Euthymios Zigabenos and an abjuration formula (used for converts from Islam). The quality of the translation into (essentially demotic) Greek is indifferent, with false renderings of individual words. But, as the editors' introductions signal, the effect of Förstel's assembling and collation of the fragments is to reaffirm E. Trapp's linguistic investigations, undertaken some thirty years ago. The pattern of quotations taken from the Koran is fairly evenly distributed, the allusions to points made in the Koran are quite summary, and the translation's quality is, for better or worse, quite consistent. It is therefore most probable that a complete translation of the Koran was available to the Byzantines for polemical and other purposes from a fairly early date; so would-be polemicists did not have to call upon readers of Arabic to make fresh translations or exegeses for them. This finding will have considerable resonance for the study of Byzantino-Arabica.