In the present paper the karyotypes of four diploids and one tetraploid species of Hippeastrum (Amaryllidaceae) are described. The nomenclature used for chromosome morphology, is that proposed by Levan et al. (1964): m chromosome (Centromeric index Ci = short arm × 100/total chromosome length = 50-37.5), sm chromosome (Ci = 37.5-25) and st chromosome (Ci = 25-12.5). The nomenclature proposed by Battaglia (1955), for the description of chromosomes with satellite was used. The results obtained are: H. argentinum (Pax) Hunz.: 2n = 22, 8 m + 8 sm + 6 st; H. rutilum (Lam.) Herb.: 2n = 22, 8 m + 8 sm + 6 st; H. agliae (Cast.) Hunz. et Coc.: 2n = 22, 8 m + 8 sm + 6 st, in these three karyotypes the pair st nọ 10 has a terminal microsatellite in the short arm (Figs. 1, 2, 3, 4). H. vittatum (L'Herit.) Herb.: 2n = 22, 8 m + 6 m + 8 st, the pair st nọ 11 has a terminal microsatellite in the short arm (Figs. 2, 4). H. petiolatum Pax: 2n = 44, 16 m + 16 sm + 12 st. All the karyotypes are bimodal because m chromosomes are shorter than sm and st chromosomes (Figs. 1, 2). In general, the species studied here had the same basic karyotype (4 m + 4sm + 3 st), only H. vittatum possesses a derived karyotype involving small changes. This basic karyotype is common to the eight species in which the karyotype has been studied. Because of this, we can consider this karyotype as fundamental in Hippeastrum. In a single individual of H. argentinum a heteromorphic pair of chromosomes was found. So far 25 species of the genus have been studied cytologically, 21 of these have only diploid level. The scarcity of polyploidy in the genus (16 %) might be a consequence of the absence of chromosome repatterning in a primary speciation (Cuadros 1, 2). Results of other authors concerning cytological data are also discussed.