The Ribosomal Database Project (RDP-II) continues to expand its collection of ribosomal RNA (rRNA) sequences and improve its analysis tools. In its June 1, 2000 release (Release 8.0), RDP-II includes 16,277 aligned prokaryotic small subunit (SSU) rRNA sequences, with about 75% longer than 899 bp. The number of eukaryotic and mitochondrial SSU rRNA sequences remains at 2,055 and 1,503, respectively. RDP-II now offers an RDP-II mirror site in Japan and provides aligned and annotated rRNA sequences, phylogenetic trees, taxonomic hierarchies, and various analysis services through its WWW server. These services include rRNA probe checking, phylogenetic placement, chimeric sequence screening, automated alignment, similarity matrix generation, and support for terminal restriction fragment polymorphism experiments. The project also plans future upgrades to its WWW analysis programs, including an improved sequence selection tool and a new phylogenetic tree creation program. RDP-II is supported by the National Science Foundation, the US Department of Energy, and the State of Michigan.The Ribosomal Database Project (RDP-II) continues to expand its collection of ribosomal RNA (rRNA) sequences and improve its analysis tools. In its June 1, 2000 release (Release 8.0), RDP-II includes 16,277 aligned prokaryotic small subunit (SSU) rRNA sequences, with about 75% longer than 899 bp. The number of eukaryotic and mitochondrial SSU rRNA sequences remains at 2,055 and 1,503, respectively. RDP-II now offers an RDP-II mirror site in Japan and provides aligned and annotated rRNA sequences, phylogenetic trees, taxonomic hierarchies, and various analysis services through its WWW server. These services include rRNA probe checking, phylogenetic placement, chimeric sequence screening, automated alignment, similarity matrix generation, and support for terminal restriction fragment polymorphism experiments. The project also plans future upgrades to its WWW analysis programs, including an improved sequence selection tool and a new phylogenetic tree creation program. RDP-II is supported by the National Science Foundation, the US Department of Energy, and the State of Michigan.