The emergence of the first human cases of avian influenza in Hong Kong in 1997 has raised fears of a new pandemic originating from the Asian continent. Despite unprecedented international mobilization, first to stop then to limit its diffusion, the highly pathogenic avian virus A/H5N1 has successfully spread in Asia, Europe and Africa by successive epizootic outbreaks affecting migratory birds and poultry, Transmission from animals to humans is uncommon but severe with a fatality rate exceeding 60% in confirmed cases. Nearly half of the countries struck by the disease is in Asia. With 87% of confirmed cases and 91% of deaths, Asia is also one of the continent most heavily affected. Like the neighbouring countries in South-East Asia, Cambodia has been repeatedly hit by avian flu in the recent years. The measures implemented to prevent the spread of A/H5N1 virus in farms, to improve the behaviour of farmers and to clean up the poultry markets emphasize the multiple difficulties to control this zoonosis. Meanwhile, influenza surveillance is being carried out in humans, based on a reporting system and a network of sentinel hospitals connected to the Institut Pasteur du Cambodge. Thus, Cambodia takes an active part in the wide international network which should quickly detect any mutational event among avian flu viruses that might lead to the emergence of a pandemic.