Rice Mutant Database (RMD, http://rmd.ncpgr.cn) is an archive for collecting, managing and searching information of the T-DNA insertion mutants generated by an enhancer trap system. We have generated approximately 129 000 rice mutant (enhancer trap) lines that are now being gathered in the database. Information collected in RMD includes mutant phenotypes, reporter-gene expression patterns, flanking sequences of T-DNA insertional sites, seed availability and others, and can be searched by respective ID, keyword, nucleotide sequence or protein sequence on the website. This database is both a mutant collection for identifying novel genes and regulatory elements and a pattern line collection for ectopic expression of target gene in specific tissue or at specific growth stage.