A free knowledgebase of chemical modulators with documented modulatory activity for epigenome reader domains. ChEpiMod organizes information about chemical modulators and their associated binding-affinity data, as well as available structures of epigenome readers from the Protein Data Bank. The data are gathered from the literature and patents. Entries are supplemented by annotation. The current version of ChEpiMod covers six epigenome reader domain families (Bromodomain, PHD finger, Chromodomain, MBT, PWWP and Tudor). The database can be used to browse existing chemical modulators and bioactivity data, as well as, all available structures of readers and their molecular interactions.