A morphological and cytotaxonomic analysis of Alstroemeria patagonica Phil. populations is made, from the Chilean Patagonian steppe, in order to clarify questions about the variability of this taxonomic entity. 3 populations were analyzed (Estancia Baño Nuevo, Jeinimeni and Estancia Chacabuco). A detailed morphological study was conducted on field specimens collected for this purpose, plus samples of the SGO and CONC herbaria. In addition, a cytotaxonomic study from collected populations was performed, using the chromosomes as a source of taxonomic evidence. Results were compared with data from Alstroemeria pygmaea Herb., in order to clarify the differences between these unifloral taxa and those with yellow flowers. The study results in the recognition of a new species of Alstroemeria for Chile and Argentina.