The relation between the percentage of dietary Calories derived from protein (P) and the corresponding net protein utilization (N.P.U. or U) was studied with various proteins of different nutritional value. At P > 40 the experimental results (from rats) did not fit the Miller–Payne linear model. A semilogarithmic plot, however, accommodated all the data, ranging from P = 10 to P = 80. The new model yields, by extrapolation, values of maximum utilization that agree well with the protein (chemical) scores. A general prediction equation is given that enables N.P.U. to be calculated from a knowledge of P and of the chemical score of the protein or protein mixture at issue.