Background - In the light of loss of mangrove forests and related biodiversity world-wide the overall objective of the online 'Mangrove Reference Database and Herbarium' is to give a current and historic overview of the global, regional and particularly the local distribution of true mangrove species. Databasing and website construction - All data are based on records containing species location information of all mangrove species (approximately 75). All the mangrove zones around the world are recorded in this database and a species list is available for the sites that have been studied or sampled. In addition, the database provides written and visual information on plant physiognomy, ecological adaptations to the intertidal mangrove habitat and nomenclature. Images of herbarium specimens are included as vouchers. Objectives - The website (http://www.vliz.be/vmdcdata/mangroves/) wants: (1) to offer a relational database for all true mangrove plant species using an expandable taxonomic tree; (2) to display a fact sheet for each mangrove plant species; (3) to present a searchable online distribution map for each species based on point-locations submitted by researchers world-wide in order to display historic as well as current distribution maps using a GIS-interface; (4) to preserve a herbarium reference specimen for each true mangrove species; and (5) to provide an automated determination key to identify mangroves world-wide. Results - The result is a functional database that can be rapidly updated and that provides information for research, management and conservation projects on the world's mangroves (biogeographical, forest management or ecological restoration in the light of species present). © 2010 National Botanic Garden of Belgium and Royal Botanical Society of Belgium.