AbstractPart I. The historical development of the use of glycerinated fats in baking is traced and some essential differences between American and British practice are discussed. Glycerinated fat comprises mixtures of mono‐, di‐ and tri‐esters; it is commonly but incorrectly called ‘glyceryl monostearate’ and the commercial material in this country, known as GMS, usually contains about 30‐40% of glyceryl monostearate or about 20% of glyceryl mono‐oleate. The effect of GMS products of varying composition on selected properties of bread, sponges and Madeira cakes is described.Specifications for the most suitable types of GMS for use in these products are discussed and the effect that various flour improvers have on the quantities of GMS showing optimum improving effect is described.Various theories that have been propounded to explain the mechanism of the action of fats, oils and GMS as crumb‐softening and anti‐staling agents are critically examined; the view is put forward that greater attention should be paid to the distribution of labile water between the coagulated gluten network and starch gel which comprise the system referred to as bread.Part II. The effect of flour oils in bread making and the influence these substances have on the improving action of the glycerinated fats are discussed. Experiments are described which indicate the presence of monoglycerides in (a) oils extracted from 81%‐extraction flour treated in various ways, (b) oils extracted from bread baked from the severally treated flours and by the aeration process and (c) fats normally used in baking and breads containing these fats. The periodic acid method of estimating monoglycerides in fatty materials is critically examined. The presence of small quantities of monoglycerides in certain of the above materials has been established by applying countercurrent extraction methods and by preparing the 2 : 4‐dinitrophenylhydrazine derivatives of the reaction products in the chloroform layer after periodic acid assay, and by applying other methods of characterization. The influence the various findings have on the pharmacological considerations involved in the inclusion of glycerinated fats (GMS) in baked products is discussed, and in particular the relationship of this information to the concept of ‘hundredfold’ acceptability advocated by Frazer as one of the main criteria in assessing the absence of risk in the use of food additives. As there is also no direct indication of cumulation of glyceryl monostearate in the body, or of any significant nutritional defect caused by the use of GMS in the manner recommended by the authors, it is concluded that the use of glycerinated fats, within reasonable limits, in baked goods involves no ris