In this paper transcriptional factor IDA (TFIIIA) has been used as a probe for identity of three-dimensional-structure of eukaryotic 5S rRNAs. I was interested in finding a common motif in plant and Xenopus 5S rRNAs for TFIIIA recognition. I found that the two eukaryotic 5S rRNAs (from wheat germ and lupin seeds) are recognized by X. laevis TFIIIA and the data clearly suggest that these 5S rRNAs have very similar if not identical three-dimensional structures. Also effects of various conditions on stability of these complexes have been studied.