“Epistolary styles” of Pseudo-Libanius (abbr. PL1), an ancient treatise on letter writing of the 5th century, includes a theoretical introduction and sample letters. The examples refer to 41 types, as a rule, one example per type. Whereas the treatise itself, which forms the basis of ancient epistolary theory, has been studied well enough, its Byzantine and post-Byzantine versions have not been studied at all. In this article, one of these versions is analyzed – a collection of sample letters compiled on the basis of Pseudo-Libanius (abbr. PL2). Our research includes the following aspects: 1) Content and style of PL2. The names of the types, represented in PL2, and the texts of the samples, go back, mainly, to the treatise of Pseudo-Libanius. The method of reworking the source is analyzed: the text is expanded by rhetorical means – epithets, comparisons, proverbs and citations are regularly introduced. 2) The PL2 manuscript tradition. Mss. PL2, as a rule, coincides with the treatise of Pseudo-Libanius and enters into various combinations with it. Depending on the structure of the text, PL2-mss. are divided into 5 classes. The characteristic of each manuscript is given: not only of the treatise itself, but also its context in mss. is taken into account. 3) The PL2 text history. An attempt is made to reconstruct the archetype of PL2: it is demonstrated that initially it was not an appendix to “Epistolary Styles”, but an independent collection of sample letters. Its supposed date is the 10th century. 4) The purpose and function of PL2. It is assumed that PL2 was written in order to update the ancient sample letters. In mss. PL2 often acts as a transitional link between the simplest examples of Pseudo-Libanius and authentic letters of Byzantine authors. Perhaps the treatise was also used as a school textbook. In the Appendix all sample letters included in PL2, with their names and incipit, are listed. The critical edition of “Epistolary Styles” and all their Byzantine versions is being now prepared by the author of this article.