In a study of the specific effects of meats and other protein foods on the iron content of the growing albino rat 74 individuals were fed, in most cases individually, from the time of weaning for periods usually of 5 weeks, after which iron was quantitatively determined in the entire bodies minus the alimentary tract. The following protein foods were compared: Skim milk powder, whole milk powder, beef muscle, beef kidney, beef brain, beef liver, navy beans, hen's egg, and peanuts. The diets were so compounded that in each case a single protein food constituted the sole source of protein and of iron, these foods being used in quantities supplying the same amounts of protein; the iron content of each diet being that which naturally accompanied the protein food used or, in other cases, an amount controlled by supplementing the quantity of iron naturally present in a protein food by adding ash of the same product. The meats were fed ground and dried, after preparation with the aid of a phosphor-bronze knife and meat chopper. Iron was determined by an adaptation of the colorimetric thiocyanate method of Marriott and Wolf. The growth from diets in which the sole source of protein and iron was skim milk powder or whole milk powder was excellent, but in the course of 5 weeks' feeding the iron content of the bodies of the rats was reduced to approximately 50 per cent of the normal. After feeding for seven months on the diet in which skim milk constituted the sole source of protein and iron, female rats were unable to rear their young. The growth from the egg diets was excellent; from the muscle, liver, and kidney diets was fair; and from the brain, bean, and peanut diets was poor. The iron content of the rats which recieved the meat foods was apparently normal in each case; the iron content of the rats which received egg was much lower, the iron content of egg apparently being less efficiently utilized than that of the meats; and the iron content of the rats which received peanuts being the lowest of all, the iron content of peanuts being especially low. Each of the seven protein foods studied, other than milk, was much superior to milk as a source of dietary iron for growing rats. There is ground for question as to the validity of the apparent specific effects of the protein foods studied, especially of egg and peanuts, by reason of the facts that the gains in body weight in the several experimental lots were very different, and that determinations were not made of the moisture and fat contents of the bodies of the rats; the existence of milk anemia, however, is certainly well established. There was no evidence of the utilization of supplementary iron, in the form of ash of muscle, brain, liver, navy bean, and egg.