This article deals with the structure of the pastoral economy of East Trans–Baikalian Buryats (Aginsky region). The herd structure used to include the five basic species of domestic animals of Eurasia: sheep, cattle, horses and, more rarely, goats and camels. A horse was of the utmost economic and status significance. However, the quantity of sheep and goats was larger. The pastoral groups owned the land and the nomads migrated with their herds along their traditional seasonal routes. In the last quarter of the nineteenth century, the influence of the Russian economy on the Buryat nomadic economy began to increase. In the USSR, these processes were more intensive. A complete sedenterisation of Buryat society took place. Agriculture was developed and nearly one-quarter of the pastures were used as arable lands. The pastoral economy changed from subsistence to one that was guided by the market. Since wool and meat were valuable commodities new breeds of sheep were raised, and the number of sheep increased greatly thereby giving rise to degradation of pastures. The ecological crisis did not develop on a large scale only because political (collapse of the USSR) and economic crises were ahead of it. As a result, the cattle-breeding and livestock economies of the Aginsky Buryats have fallen into decay. At present, although a crisis situation has been held back, progress is not observed.