This substantial notice provides a clear overall description of the wide Central region known as Yeti Su (Russian: Semirech’e), comprising the lands north of Transoxiana which stretched from the basin of the Issyk-Kul lake northwards to the Lake Balkhash. The author gives a historical overview of the region through a wide range of primary sources. Whence Chinese annals and travel accounts (by Xuan Zang) document the period prior to the concomitant Arabs’ and Turks’ penetration of Transoxiana, the Islamic geographers of the tenth century onwards mention the Qarluqs and other Turkic tribes for their long resistance to Islam. Among the latter, the Qarakhanids, after they became Muslim, were to use the Yeti Su as a base for their take-over of Transoxiana. They were followed in the mid-eleventh century by the proto-Mongol Buddhist Qara-Khitays, succeeded themselves by Naymans, then Chingizid Mongols in the early thirteenth century. The latter’s rule showed favourable to the adherents of non-Muslim faiths, among whom the Nestorians (see their important cemeteries at Toqmaq and Pishpek), the Chaghatayid khans resisting conversion to Islam until the mid-fourteenth century. Soon after the Timurid episode, the Buddhist Mongol Oirats (called by the Muslims Qalmuqs) were to become an enduring factor in the history of the region. As a result of endless unrest, Chinese sources of the fifteenth century no longer speak of flourishing towns and villages in Yeti Su, but exclusively of land inhabited by nomads who dwelt in tents. In the early sixteenth century pagan Kyrgyz first moved from the upper Yenissei to this region, this being the first attestation of this people in the neighbourhood of what has become their modern home, present-day Kyrgyzstan. In spite of attacks by the Turco-Mongol amirs of Transoxiana, the Qalmuqs dominated Yeti Su until the mid-eighteenth century, when Chinese armies came westward and overthrew them: The Kyrgyz and Kazakhs were now virtually independent, until the armies of Imperial Russia advanced through the Kazakh Steppe. The last paragraphs of the notice describe the establishment of the modern frontiers between the Russian and Chinese Empires, and the creation of new administrative entities in the Yeti Su by the Russian colonial and Soviet powers. The very short bibliography is compensated by reference to a number of other notices of the Encyclopaedia of Islam.