Sendai virus (SeV), also known as murine parainfluenza virus type 1, is a negative sense, single-stranded RNA virus of the paramyxovirus subfamily Paramyxovirinae, genus Respirovirus, members of which primarily infect mammals. It was originally recovered in Sendai, Japan, so it is also called hemagglutinating virus of Japan (HVJ). SeV is responsible for a highly transmissible respiratory tract infection in mice, hamsters, guinea pigs, rats, and occasionally pigs, with infection passing through both air and direct contact routes. The virus can be detected in mouse colonies worldwide, generally in suckling to young adult mice. It is believed that the natural host of Sendai virus is the mouse and that the virus is usually nonpathogenic for humans. The SeV genome is organized starting with the short 3’ leader region, followed by six genes encoding the nucleocapsid protein (NP), phosphoprotein (P), matrix protein (M), fusion protein (F), hemagglutinin-neuraminidase protein (HN), and large protein (L), and ending with a short 5’ trailer region. The SeV now has been developed as gene transfer vectors for expressing foreign genes to a wide range of mammalian cells and tissues with high efficiency.