MAGEST is a database for newly identified maternal cDNAs of the ascidian, Halocynthia roretzi, which aims to examine the population of the mRNAs. We have collected 3 and 5 tag sequences of mRNAs and their expression data from whole-mount in situ hybridization in early embryos. To date, we have determined more than 2000 tag-sequences of H.roretzi cDNAs and input them into public databases. The tag sequences and the expression data as well as additional information can be obtained through MAGEST via the WWW at http://www.genome.ad.jp/magest/