The diatribe is a mode of exposition that grew out of the teaching of the popular philosophers of the Hellenistic and Roman period. It was adopted by St. Paul in his epistles and by the Church Fathers, first of all by John Chrysostom. In a diatribe, the author presents his thoughts in the form of an argumentative dialogue with an imaginary interlocutor; moreover, this dialogue is not narrated, but acted out, the author speaking both on behalf of himself and his opponent. Some characteristic features of the diatribe are the frequent use of the parenthetical φησί ‘says (the imaginary opponent)’, the formulas τί οὖν ‘what then?’ (to introduce a false conclusion) and μὴ γένοιτο ‘far be it from me’ (to reject it), questions such as asὁρᾷς ‘don’t you see?’ and vocatives such as ἄνθρωπε ‘man’. 
 The diatribe entered medieval Orthodox Slavic writing through the translations of the New Testament and the Church fathers. This paper examines the impact of the diatribe on original texts written by two of the most prominent authors of the Slavic Middle Ages: Kosmas the Presbyter and Grigorij Camblak. 
 Kosmas the Presbyter wrote his Sermon Against the Newly-Appeared Heresy of Bogomil in the second half of the 10th century. This work combines a pedagogical (instruction to the believers) with a polemical layer (refutation of the “heretics”). In a handful of passages, the transition from the first to the second layer exhibits the typical features of diatribe: Kosmas introduces a counterargument by the imaginary opponent by parenthetical рече (φησί) and then addresses this opponent directly in order to refute him. Most of the time, however, the transition from the pedagogical to the polemical layer is less smooth. All in all, Kosmas’s diatribal style does not reach the smoothness of his Chrysostomic models. 
 Grigorij Camblak is the author of a number of homilies that he delivered in the late 14th-early 15th century. Seven of the published homilies attributed to him show a variety of diatribal formulas, which are investigated in more detail. Their function in the polemical discourse is compared to that of the original Hellenistic, Biblical and Patristic diatribal formulas in Greek. Grigorij Camblak’s spontaneous use of these formulas in his original Slavic compositions shows that he internalized the polemical and didactic strategies of the diatribe and found ways to express its functions in Slavic. Some of his homilies indeed approach or even equal the level of Chrysostom’s diatribal style.