Separate geographic forms of sea buckthorn (Hippophaë rhamnoides L.) are characterized not only by different composition of triacylglycerols (TAGs) of their fruit mesocarp oil, but also by a different biosynthetic pattern of the TAGs. Siberian, Central Asian, and Baltic forms contain TAGs, which include mostly hexadecenoic (C 16:1 ) and palmitic (C 16:0 ) fatty acid (FA) residues and are synthesized according to the theory of 1,3-Random, 2-Random Distribution of FAs between the respective OH groups of glycerol. At the same time, the mechanism of formation of TAGs of the Caucasian form rich in the residues of C 16:0 and octadecenoic acid (C 18:1 ) is in accordance with the theory of Restricted Random Distribution of FAs. The occurrence of two different patterns of TAG biosynthesis in the mesocarp of the same biological object is demonstrated here for the first time. As for seed oils, the geographic forms studied here virtually do not differ from each other in the FA composition of their TAGs.