The set of polypeptides was studied after translation of soybean seed mRNA in rabbit reticulocyte system. Storage proteins of soybean-glycinin and conglycinin are synthesized as a high-MW precursors. The precursors of mature subunits of glycinin had a MW approaching the sum of MW of basic and acidic subunits; the precursors of conglycinin were 8000 daltons longer than mature ones. The mRNA sequences were cloned after reverse transcription into pBR322. The c[complementary]DNA clones containing the structural sequences of 2 subunits of conglycinin. The glycinin precursor and 8800 dalton polypeptide were identified by hybrid-selection procedure. A portion of the gene of one conglycinin subunit was sequenced.