Adjusting the pH of the dilute tris(hydroxymethyl)aminomethane buffer extract of defatted soybean meal to 6.6 causes precipitation of the 11S globulin. Factors affecting the precipitation (namely, pH, Tris concentration, protein concentration, and ionic strength) were investigated in order to determine the optimum condition for simultaneous fractionation of the 7S and 11S globulins. It was found that the two globulins could be fractionated by their different solubilities in dilute Tris buffers. Protein concentration and NaCl (up to 0.04 M) had no noticeable effects on the separation of the two globulins. These results led to a simple, large-scale method for fractionation of the two globulins and whey proteins.Defatted soybean meal was extracted with 0.03 M Tris-HCl buffer (pH 8.0). The 11S globulin was precipitated at pH 6.4. The 7S globulin was separated from whey proteins by isoelectric precipitation at pH 4.8. Ultracentrifugal analyses, disc electrophoresis, and immunodiffusion indicated very little cross-contamination between the prepared fractions.