Cool Stars 14 - Submitted Abstract # 280 This version created on 05 October 2006 Discovery and characterization of Brown Dwarfs using Virtual Observatory tools. Enrique Solano, INTA-LAEFF, Madrid, Spain Eduardo MartÃn, IAC, Spain Jose A. Caballero, MPI, Heidelberg, Germany M. Luisa Valdivielso, IAC, Spain David Barrado y Navascues, INTA-LAEFF, Madrid, Spain Brown dwarfs are intrinsically faint objects so their detection is not straightforward. Although the advent of global surveys at deep optical and near-infrared wavebands like 2MASS, SDSS or DENIS allowed mining the sky through an appropriate combination of colours and/or proper motion information alleviating, at least partly, this situation, the reality is that building a census of substellar objects implies the discovery of a statistically significant number of them through queries that combine attributes available from different archives, an approach out of the scope of the "classical" research methodology but that perfectly fits in the framewok of the Virtual Observatory as demonstrated by the discovery of a new L-type brown dwarf during the 2003 NVO Science Demonstration. Also, the characterization of the stellar mass function at the lower end has been identified as a key Science Case by two of the most important VO initiatives: AstroGrid and EURO-VO. In this poster we describe the methodology and lines of work that, in the field of detection and characterization of brown dwarfs, are being developed in the framework of the Spanish Virtual Observatory. ----------------------------------