The last glacial maximum and late glacial environmental and climatic variability in the Baikal region, southern Siberia, Russia has been studied in a sediment sequence from Lake Kotokel, located 2 km east of Lake Baikal, using the oxygen isotope composition of diatom silica (d18Odiatom). The purification of diatom frustules involved the process of trimethylsilylation, which has been shown to be suitable for preparation of diatoms for oxygen isotope analysis. The Lake Kotokel d18Odiatom record presented here spans intervals from about 24.6 to 22.9 ka BP (further referred to as ‘last glacial maximum’) and ~16.7-11.5 ka BP (further referred to as ‘late glacial’) displaying variations in the oxygen isotope composition between +26.7 and +31.2‰. Overall high d18Odiatom values of about +29 to +31‰ during the two investigated intervals characterize a strongly evaporative lake system in a dry environment and suggest a lower than present lake level due to enhanced evaporation. The Lake Kotokel diatom isotope record is roughly in line with the 60° N summer solar insolation, pointing to a linkage to broader-scale climate change, but displays weaker reaction to short-term climatic oscillations, i.e. Bølling-Allerød or Younger Dryas. The climate warming at ~14.3 ka BP is marked by negative spikes in the d18Odiatom record due to isotopically low melt water input from the mountainous hinterland.