5S ribosomal RNA is an integral component of the large subunit of all cytoplasmic and most organellar ribosomes. Its small size and association with ribosomal as well as non-ribosomal proteins made it an ideal model RNA molecule for studies of RNA structure and RNA-protein interactions. 5S Ribosomal RNA Database provides information on nucleotide sequences of 5S rRNAs and their genes. The sequences for particular organisms can be retrieved as single files using a taxonomic browser or in multiple sequence structural alignments. The database is available on line at http://biobases.ibch.poznan.pl/5SData/ .