Absorption and assimilation of some of fatty acids and fatty acid composition of platelet lipids and red cell stroma were studied in 75 patients suffering from the malabsorption syndrome. The patients were distributed in 4 groups in terms of the disease severity. The patients subjected to an extensive resection of the small intestine and those with stage III enterocolitis manifested malabsorption, because of significant steatorrhea, of food polyunsaturated fatty acids, particularly of linoleic acid. This led to the deranged formation of lipid structures of biomembranes, which is evidenced by the magnitudes of the essential metabolism ratio (EMR). The disease severity was in good agreement with the intensity of steatorrhea and the decrease of EMR. The data obtained form the basis for recommendations on an adequate fatty acid composition of the diet designed for patients with the malabsorption syndrome. It is thus recommended that the diet should include fat products rich in fatty acids with a short- and medium-size carbon chain, oils rich in oleic acid, and be supplemented as well with polyunsaturated fatty acids in the concentrated form ("essentiale" preparations).