The idea that the Nothofagus genus formed part of the Chilean southern-temperate floristic elements which originated in the southern end of the Gondwana continent about 45 million years ago is discussed. Both the present and the past distribution of the genus in South America and Australasia are given; the latter is not in agreement with the small dispersive capacity of the genus. Therefore, Nothofagus' possible origin is discussed. The chilean taxa are named, discribing the reproductive and vegetative morphology. On the basis of this information, three ecological groups are presented: decidous species of large leaves typical of the mediterranean region of Central Chile, decidous species of small leaves from the subantarctic region and perennials of small leaves that live in the Valdivian region. The names of the participans in the "Biology of the Nothofagus Genus" symposium are listed. The Symposium was held during the IV National Congress of Botany in Valdivia (Chile) in September 1986.