Total RNA was isolated from the fungus Schizophyllum commune and translated in a wheat germ and a rabbit reticulocyte cell-free system. The in vitro products were analysed by two-dimensional gel electrophoresis. Both systems synthesized more than 600 distinct polypeptides, the vast majority of which (about 80%) was qualitatively and quantitatively the same. This demonstrates that the plant and animal system are very similar with respect to their specificity and efficiency in translating heterologous RNA. The patterns of proteins synthesized in vivo markedly differed from those produced in vitro; only 40% of the protein spots coincided on the gels. On the average the in vivo proteins were smaller.