There is evidence that some influenza pandemics are caused by influenza viruses which have acquired new antigens from avian viruses. In order to understand the conditions under which antigens are transferred between animals and human strains of influenza viruses it is necessary to study the ecology of animal influenza viruses. Antibodies to influenza virus found in Adelie penguins at Casey Station ... and in skuas at Cape Bird indicate that influenza viruses infect birds in the Antarctic. The aim of this study was to isolate the influenza viruses from Adelie penguins and skuas, characterize them and compare them with influenza viruses from other hosts and from other regions. In addition, Weddell seals were sampled to determine if they are hosts to these viruses. Recent outbreaks of serious disease in seals in the northern hemisphere were caused by what had been regarded as avian influenza viruses. If these outbreaks were caused by direct transfer from a bird to a mammal it raises the question if a similar transfer could occur to humans causing a serious and widespread epidemic. Therefore, whether seals are hosts to these viruses or whether the recent isolates were introduced to mammals from the influenze virus pool of aquatic birds was determined. Cloacal swabs and blood and tissue samples were collected from 168 Adelie penguins, 200 skuas and 100 Weddell seals.