Four cereal products prepared as “breakfast foods” have been studied with reference to the biological value for human subjects of the contained proteins based on egg protein as standard. Two of the products were whole oat preparations; one, three-quarters oats; and one, whole wheat with “all of the original nutrients retained.” The egg replacement method as previously employed in this laboratory was followed and some improvements were made. The squad was divided into two groups, which ate the cereals in reverse order, thereby counteracting any advantage from mere position in the series of 9 periods — 5 on egg, 4 on cereals. The biological values of the cereal proteins were calculated for each individual on the basis of his average data from all the egg periods. Hence, each cereal food occupied the same average distance from the nitrogenous midpoint of the series of standard diets. After calculation of the biological values and the replacement values in terms of the egg standard, and obtaining standard deviations, the extreme variants for each cereal were eliminated in accordance with standard statistical procedure. The biological values relative to egg protein of the 4 cereal products recalculated with their standard deviations for the number of subjects retained were found to be as follows: no. 1 oats 89.9 (3.81), no. 2 oats 88.1 (5.56), puffed (or “exploded”) oats-corn-rye cereal 82.8 (6.52), and flaked wheat 76.7 (5.85). The differences between the means for the two oats products and wheat flakes are highly significant, as is also true for the no. 1 oats and the puffed oats-corn-rye cereal but not for the latter and wheat flakes. The replacement value, defined as the extent to which any particular protein can replace egg protein in the maintenance of nitrogen balance, was calculated for each group of subjects for each cereal. The order of values derived from weighted differences in average N balances between cereal and egg are as follows: no. 1 oats 79.6 (7.2); no. 2 oats 80.7 (8.3); puffed oats-corn-rye mixture 75.5 (5.9), and wheat flakes 67.3 (6.6). Only the differences of means between the two whole oats products and wheat flakes are statistically significant.