Based on the authors' long-term research, systematization and generalization of soil and cartographic materials of SIFBR SB RAS, as well as the use of a large number of literature and archive sources, the monograph characterizes the soil formation conditions and soil cover of the Irkutsk region. It is shown that due to the great length of the region's territory from north to south and from west to east, considerable heterogeneity of relief, geological structure, climatic conditions and vegetation, the soil cover is characterized by a complex structure and a great variety of soil types. On the basis of the newest researches and modern representations about genesis of soils the systematic description of soils and their diagnostics are given, specific features of temperature and water regimes of seasonally frozen soils, structure of a soil profile are marked. A new scheme of soil-geographical zoning of the Irkutsk region territory, which was laid in the basis of the soil map of the Irkutsk region in scale 1:1 500 000, published by GUGK USSR in 1988, has been worked out. The work may serve as an explanatory note for the soil map of the Irkutsk region in scale 1:1 500 000, published in 1988.