The NCBI Organelle Genome Resources is a collection of eukaryotic organelle complete genome sequences, presented as part of the NCBI Reference Sequence (RefSeq) project that provides curated sequence data and related information for the community to use as a standard. Currently, only the metazoan mitochondrial sequences are considered reviewed (manually curated). Other mitochondrial and chloroplast sequences are provisional and are presented as found in the source GenBank records. In addition to providing a list of complete mitochondrial and plastid genomes, this site also presents tools that can be used to analyse these sequences. Made available on the Web by the US National Center for Biotechnology Information (NCBI).