Stable isotope analyses of soils significantly contribute to a better understanding of biogeochemical and paleoenvironmental processes. This paper presents and discusses stable carbon, nitrogen and oxygen isotope (δ¹³C, δ¹⁵N and δ¹⁸O) data of representative soils of Buryatia, southern Siberia. In undisturbed soils (kastanozem, phaeozem, gleysol, podzol, leptosol) δ¹³C and δ¹⁵N values of soil organic matter (SOM) increase from the organic layers (O-layers) to the mineral topsoils (A_h-horizons) and subsoils. This primarily indicates advanced C and N-mineralization in lower soil horizons and reflects the input of fresh litter in the O-layers. Combined with numerical ages, these data indicate that during the last ca. 40 ka no C4 grasses prevailed in semiarid regions of Buryatia. Disturbed soils (ploughed chernozem and an anthrosol) do not show with depth increasing δ¹³C and δ¹⁵N values but are characterized by fluctuating depth profiles. High δ¹⁵N values in the anthrosol (up to 10.5‰) point to an open N cycle. In a middle and late Holocene aeolian paleosol record (Burdukovo), δ¹⁸O of the hemicellulose-biomarkers arabinose and xylose show minima in the dark humic buried A horizons and maxima in the greyish silty fine sand layers. This reflects the alternation of more arid and more humid conditions. This interpretation is also in agreement with higher grain size ratios (20-63 μm)/(2-6 μm) in the greyish fine sand layers, documenting increased wind strength and dust supply. SOM δ¹³C and δ¹⁵N values of O-layers and A_h-horizons were furthermore investigated along an altitudinal transect in the Khamar Daban Mts (from 470 m to 1800 m a.s.l.). Generally, δ¹⁵N values decrease with increasing altitude giving evidence of more closed N cycles at higher altitudes, which are characterized by lower temperatures. As an exception, δ¹⁵N of the A_h-horizons above 1500 m reveals conspicuously positive values, presumably because of frequent burning of the dwarf pine belt with high N losses due to volatilization. δ¹³C shows no significant altitudinal trend above 750 m a.s.l., but more negative values below 750 m a.s.l. This may be attributed to frequent temperature inversions close to Lake Baikal. Similarly, this inversion inducing fog and higher humidity close to Lake Baikal could also explain why δ¹⁸O of the hemicellulose-biomarkers arabinose and xylose do not reflect the 'altitude-effect' as it could be expected from δ¹⁸O of precipitation.