A study has been made of features of the ozonolysis of natural bitumen of the Mortuk field (West Kazakhstan) as a function of the nature of the solvent used (burning kerosine, toluene) and the degree of conversion (total ozone consumption), When the reaction is carried out in kerosine, a precipitate is formed which can readily be removed by decanting and amounts to 32 wt.% of the sum of the products. No solid phase formation is observed when the process is carried out in toluene. The overall product yields in both cases increase with an increasing extent of the process through the addition of oxygen atoms to the initial molecules, and with an ozone consumption of 100 g/kg raw bitumen they exceed the quantity of the latter by 6-11 wt.%, An important result of the process is a considerable reduction in the degree of aromaticity of the molecules owing to degradation of the condensed polyarene structures. Adsorption separation of the soluble reaction products makes it possible to produce, in the form of hexane eluates in yields of up to 43% (in kerosine) or 52% (in toluene), oils extensively purified of polycycloaromatic and (when the process is carried out in kerosine) heteroatomic compounds. Polar products of conversion with the oils removed can be used in practice as highly effective cheap de-emulsifiers and structure formers of soils.