Variability in chilean Nothofagus species, expressed as more or less apparent differences between populations, has its origin on the broad distribution and on the habitat diversity of them. Furthermore they easily hybridize when two different species grow together in ecotones, developing fertile hybrids able to introduce new variation factors derived from introgression phenomena. Based on these factors variation found in Nothofagus obliqua, N. alpina and N. dombeyi is discussed. N. glauca and N. leoni are also mentioned in relation to N. obliqua variation and hybridization and possible introgression in its northern populations. In the same way N. nítida and N. betuloides are mentioned, because they hybridize each other and with N. dombeyi, brinding new variation causes to these Nothofagus populations. Finally morphologic types described for N. pumilio are pointed out.