The vegetation belts on the slopes of the Sierra de Catorce and surrounding areas in the southern Chihuahuan Desert (State of San Luis Potosí, México) were recognized. The major units of vegetation were studied from a phy tosociological point of view and bioclimatic data results from weather stations were analysed and extrapolated. The Tropical Xeric and Tropical Pluviseasonal bioclimates were characterized in the área. Of the first one the Semiarid Thermotropical, the Semiarid Mesotropical, the Dry Mesotropical, and the Dry Supratropical belts are present. Of the second bioclimate, only the Subhumid Supratropical belt is punctually present. The description of each of these belts is accompanied by data on composition, cliserial distribution and bioclimatic diagnosis of the corresponding potential natural vegetation (diferent forest and scrub communities) and the most representative biomarkers of each situation are indicated.
