Outer birch bark (OBB) contains an unusually high amount of extractives (35-40%), from which up to 71% is composed of a lupane type pentacyclic triterpene – betulin in the mixture with the same type triterpene – lupeol, the content of which in extractives is 3-7%. The high content of these triterpenes in OBB and their universal biological activity are the reasons for their broad-scope research. Industrial-scale isolation is hampered by the lack of simple, non-expensive isolation and purification technologies. We have tested the solubility and purity of birch OBB extractives in PE140 at its boiling temperature. Triterpenes’ solubility was 13.9 g/L and, cooling the hot filtered solution, 81% of the total extractives’ mass precipitated. The solubility of the remaining extractives in the mother liquor was 2.69 g/L. It was most interesting that the yellowish extractives obtained after the evaporation of the cooled mother liquor had a high content of lupeol, i.e. 39.7%, but there were only traces of betulin. This suggests the possibility of using fractional crystallisation for separating the triterpene mixture. Using the fractional crystallisation method and the solubility property of triterpenes, we tested their ability to concentrate lupeol in the PE140 solution and, at the same time, to purify betulin from the lupeol admixture. As a result, from the extractives that contained 11.8% of lupeol and 69.6% of betulin, two crystal fractions were obtained, namely, from the filtrate that contained 3.3% of lupeol and 89.5% of betulin, and from mother liquor, which contained 37.3% of lupeol and 2.7% of betulin. The fractional crystallisation could be a promising, non-expensive and simple method for the simultaneous concentration of lupeol in the mother liquor and the purification of betulin from the triterpene admixture.