Dengue virus (DENV) and West Nile virus (WNV), close siblings of the Flaviviridae family, are the causative agents of Dengue hemorraghic shock and West Nile meningoencephalitis respectively. Vaccines against these two flaviviruses are currently unavailable. The Dengue fever & West Nile fever Viruses are very virulent. They cost a lot of people their lives. Suburban areas of Khartoum state are agricultural areas where there are canals, with pool water that represent a good places for mosquito breeding. Mosquitoes are vectors for transmission of many viral diseases such as Dengue and West Nile viruses. Despite all these facts, very limited studies were conducted to show the seroprevlance of these two viruses.