The author analyses the corpus of source constituted by the Posol’skie knigi [Embassies’ Registers] for the understanding of diplomatic correspondence between the Noghai Horde and Muscovy. The Noghai Ulus, with its centres between the Yayik and the Lower Volga Rivers, was at the apogee of its might in the sixteenth century. The Russian state had developed a whole diplomatic and administrative device to understand the demands of its conquerors and eastern neighbours. This led to the institution, in 1549, of the Posol’skii Prikaz in charge of taking care of diplomatic documents, now preserved for the most part in Russia’s State Archive of Ancient Documents (RGADA in Russian acronyms), our main base of primary sources on Muscovy’s foreign policy. The author shows the gradual intensification of reporting activity between the Noghai Ulus and Muscovy, which passes from one book in the late fifteenth century to three in 1549 and up to a total of ten for the year 1605. The first relation is dated 1489: I. Vásáry evokes the Noghai delegation arriving with interpreters and scribes from the ranks of mullahs, living between one and three months in Moscow, and leaving accompanied with Russian envoys. One preoccupation of the Muscovite chancery seems to have consisted of making the difference between envoys (posly) sent by the Noghai sovereigns and those sent by mandatory agents (dobrye liudi or slugi). The author also deals with the redaction of documents, drafted in Saraychi by secretaries before being translated in the Kazennyi dvor. I. Vásáry remarks these documents’ shortness, concision, and high literary quality. Examples are provided from the sixteenth and seventeenth centuries with Tatar text and Russian translation.