Two-dimensional Polyacrylamide gel electrophoretic maps of ribosomal proteins isolated from soybean seedlings were constructed prior to the investigation of mRNA levels. Polysomes and ribosomal subunits were isolated from the apical hooks of 3-day-old soybean seedlings. A total of 40 and 51 basic proteins, associated with the 40S and 60S subunits, respectively, was resolved on the four different two-dimensional gel systems used in this study. The effect of the synthetic auxin (2,4-dichlorophenoxy)acetic acid (2,4-D) on ribosomal protein mRNA levels was investigated by in vitro translation of RNA isolated from 2,4-D-treated and nontreated hypocotyls. The in vitro synthesized proteins were extracted and separated by two-dimensional Polyacrylamide gel electrophoresis. Stained protein spots that corresponded to ribosomal proteins were excised from the gel, and the in vitro incorporation of [35S]methionine was determined. Results indicate that auxin induces an 8-fold increase in the relative amount of translatable ribosomal protein mRNAs.