The Sierra de Catorce located in the north of San Luis Potosí state, shelters some of the most important peaks within the Chihuahuan Desert, whose altitudes reach beyond 3000 meters. The fact that the Sierra is an important area for flora and plant community diversification in this ecoregion has been favoured by this situation. From a phytosociological study of the territory vegetation, carried out since 1999, we have extracted a preliminary checklist of the flora. Until now the vascular plants checklist is composed by 526 species and four infraespecific taxa, assambled in 293 genera and 88 families. The best represented families and genera are Asteraceae, Poaceae, Cactaceae, Fabaceae, Fagaceae, and Lamiaceae, and Quercus, Opuntia, Muhlenbergia, Salvia, Agave, Bouteloua and Dyssodia respectively. The vegetation types representative of the area which shelter the diferent taxa, are indicated. Finally, from different checklists of threatened flora, the species included in some of the recognised categories are identified.
