Zoonoses are disease and/or infection naturally transmissible between vertebrate animals and humans. Emerging zoonoses are defined by the WHO/FAO/OIE joint consultation on emerging zoonotic disease held in Geneva, 3-5 may 2004 as "diseases which are newly recognized or newly evolved or that have occurred previously but show an increase in incidence or expansion in geographical, host or vector range". The number of emerging zoonoses has increased dramatically over the last few decades, with potentially serious human and economic impact worldwide. Many factors are behind the emergence of these zoonotic diseases. Intensive animal husbandry and changes in the production and distribution of food and other commodities, climatic and environmental changes, rapid transportation of human and animals, changes in life style and increased animal contacts are some of the factors that could introduce a new disease in a particular area. Viral infectious agents are more prone to mutation and sudden or gradual change and expansion to new geographical areas or hosts. In this article we briefly discuss some of the zoonotic diseases which may have potential health effects in Iran, such as avian influenza, West Nile viruses, Rift Valley fever, Congo-Crimean hemorrhagic fever, Lassa fever, Sars, and Ebola Marburg hemorrhagic disease.