TADB (http://bioinfo-mml.sjtu.edu.cn/TADB/) is an integrated database that provides comprehensive information about Type 2 toxin-antitoxin (TA) loci, genetic features that are richly distributed throughout bacterial and archaeal genomes. Two-gene and much less frequently three-gene Type 2 TA loci code for cognate partners that have been hypothesized or demonstrated to play key roles in stress response, bacterial physiology and stabilization of horizontally acquired genetic elements. TADB offers a unique compilation of both predicted and experimentally supported Type 2 TA loci-relevant data and currently contains 10,753 Type 2 TA gene pairs identified within 1240 prokaryotic genomes, and details of over 240 directly relevant scientific publications. A broad range of similarity search, sequence alignment, genome context browser and phylogenetic tools are readily accessible via TADB. We propose that TADB will facilitate efficient, multi-disciplinary and innovative exploration of the bacteria and archaea Type 2 TA space, better defining presently recognized TA-related phenomena and potentially even leading to yet-to-be envisaged frontiers. The TADB database, envisaged as a one-stop shop for Type 2 TA-related research, will be maintained, updated and improved regularly to ensure its ongoing maximum utility to the research community.