The concept of emerging infectious diseases appeared in the late 1980s, when major outbreaks occurred around the globe and surprised many scientists who considered infectious diseases to be maladies of the past or limited to the under-developed world. Several reports identified erosion of the public health infrastructure among the factors contributing to new and re-emerging infectious diseases, As indicated by Morse, "Disease emergence often follows ecological changes caused by human activities such as agriculture or agricultural change, migration, urbanization, deforestation, or dam building". "Among these new dis eases, surprisingly, most emergent viruses and many emergent bacteria are zoonotic". Several new zoonoses have been recently identified. Many of these diseases were either unknown? because we were not able to isolate the infectious agent or to distinguish them from other clinical syndromes, or discovered accidentally. Much of the recent identification of new pathogens has been based on new molecular biology tools or epidemiological studies. For all these diseases or infections. veterinarians played a key role in their identification, isolation of the causative organisms and understanding of the epidemiology of the infection. The role of the veterinary profession is very important in public health and on the rise again in the U.S.A., as it should be in many other countries. Surveillance, clinical curiosity and awareness, epidemiology and laboratory training are the essential tools and competency that the veterinary profession must use to meet the challenge of new emerging zoonoses. (C) 1998 Elsevier Science Ltd. All rights reserved.