The protein value of different legume foods was studied in weanling rats by determining Net protein Utilization (NPU), Protein Efficiency Ratio (PER), Biological Value (BV), Nitrogen Balance (NB) and digestibility of the protein. NPU was determined by carcass analysis and by nitrogen determination in one of the hind legs of the experimental animals. All samples were evaluated at a 10% protein level in the ration, with and without a methionine suplement. The effect of protein concentration in the diet on the protein quality determinations used was also studied in the black bean (Phaseolus vulgaris) sample. Results showed a good correlation among the several values of protein quality evaluation determined by the different methods used, indicating that any of these procedures can differentiate protein quality between samples. Likewise, it was confirmed that NPU can be as accurately calculated by nitrogen carcass analysis as by determining the nitrogen content in the hind leg of the animals. Due to its low cost and the small amount of sample required for the determination, the modified NPU method using the traditional 10-day experimental period could be very useful in determing NPU in programs dealing with the nutritional improvement of food legumes.