The aquatic surface microlayer is located at the atmosphere-hydrosphere boundary and occupies 70% of Earth's surface, covering all water bodies. The depth of the surface microlayer is about 50 μm. A special microbial community called neuston is formed there. The total bacterial abundance in the surface microlayer (SML) and underlying waters (UW) of Lake Baikal was studied using epifluorescence microscopy. Physico-chemical features of the surface microlayer of Lake Baikal were revealed for the first time.