SummaryA theory has been presented for the formation of fats which gives the amounts of the various glyceride types equivalent to a random or modified restricted random distribution and at the same time gives a predominance of specific positional isomers. The basis of the theory is a random attachment of the fatty acids at each stage of glyceride synthesis with an intramolecular rearrangement to a preferred form at the 1,2‐diglyceride level of fat formation. The theory gives a good correlation of much of the data available on glyceride structure at the present time.Like all previous theories, the present proposal is based on the analysis of the final products of fat synthesis without any definite knowledge of the mechanism of the synthesis. Much more work is required on the glyceride structure of fats and the mechanism of their biosynthesis before the distribution pattern of the fatty acids in natural fats can be definitely established.