A B S T R A C T Alstroemeria (Alstroemeriaceae) is an endemic genus of South America with two major distribution centers in the continent: Chile and Brazil. In Chile the genus is distributed from the North, near Iquique (20o13’ S, 70o09’ W) to the Chilean and Argentine Patagonia (53o10’ S, 70o54’ W). The central zone of Chile presents the highest number of species. A. presliana Herb. grows from Curico (34o59’ S, 71o14’ W) to Cautin (38o45’ S, 72o34’ W) in Chile and Neuquen (36o50’ S, 71o05’ W), Argentina. A comparative karyotype study was made between a population of A. presliana subsp. presliana and a population of A. presliana subsp. australis Ehr. Bayer. Both populations presented asymmetric karyotypes, with 2n = 2x = 16 chromosomes, but with different chromosome formulae: A. presliana subsp. presliana has a haploid formula with 4m + 1sm-sat + 1st-sat + 2t, i.e., four pairs of metacentric chromosomes, one submetacentric pair with satellite, one subtelocentric pair with satellite, and two telocentric pairs. A. presliana subsp. australis has a formula with 2m + 1m-sat + 1sm + 4t chromosomes, i.e., two pairs of metacentric chromosomes, one metacentric pair with satellite, one submetacentric pair, and four telocentric chromosomes. These results indicated that the karyotype of the subspecies is very different, and it would be possible to recognize A. presliana subsp. australis as a new species.