Now that rationing of certain articles of diet has begun in Great Britain, interest is naturally being concentrated on substitute foodstuffs. In the recent past, margarine has not enjoyed much popularity, even among the poorer people of the country. This has been due partly to a not too savoury history and partly, no doubt, to ignorance of its constitution and dietetic value. Present-day brands of margarine cannot be considered in any way Ersatz butter, but will, once prejudice has been eliminated by experience, prove complementary to the adequate amount of butter allowed under the present rationing scheme. At present, margarine is not being rationed; therefore until it becomes necessary to ration cooking fats, its greatest value lies in eking out our butter supplies.