The bee-plant community in a xeric ecosystem in northwestern Argentina was studied concerning diversity, relative abundance, floral preference and phenology. Fifty-seven bee species were recorded, 42.1% of them endemic to arid regions of southern South America, visiting flowers of 11 plant species. The most abundant bees were Canephorula apiformis (Friese, 1908), Isomalopsis niveata (Friese, 1908) and Melectoides bellus (Jorgensen, 1912). No strictly specialist bee was observed. Some aspects of bee-flowers associations and distribution patterns are discussed.