In a study of the relationship between the dynamic changes in cellular organelles and biosynthesis of soybean storage proteins, we found that as the protein componentsaccumulated, the a and a'-subunits of 7S globulin appeared first, followed successively by the acidic and basic subunits of US globulin and finally by the^-subunit of 7S globulin. Labeling experiments using tissue slices showed that the radioactivities of (3H)leucine and (14C)7V-acetyl-D-glycosamine were incorporated into the trichloroacetic acid insoluble fraction and that (14C)7V-acetyl-D-glycosamine was specifically incorporated into 7S. Soybeans have been an important protein source in Japan for centuries. They contain