Abstract : New viruses were identified and new geography and pathogenicity were recognized for already known viruses. Kagoshima virus from Japan caused congenital abnormalities in livestock and was the same as Kasba virus, previously known from India. Batai virus was found for the first time in Africa and for the first time was recognized as a cause of human disease. A new arenavirus was isolated from spleen of a fatal human case in Venezuela. In addition, studies were done to revise the taxonomy of alphaviruses. U.S. Army patrol dogs in Korea were shown to be infected frequently with Japanese encephalitis virus and acted as sentinels. By molecular techniques it was shown that the dengue-2 viruses in Venezuela and Brazil are very similar to those prevalent in Jamaica in 1981 and probably originated in Viet Nam. Vaccinia recombinant viruses with structural JE gene inserts secreted particulate antigens and were highly immunogenic. E and prM genes were needed for secretion of the particles. Immunization of 526 volunteers with inactivated JE vaccine led to uniform responses of neutralizing antibody. The laboratory distributed reagents in 1990 to 28 laboratories in 10 countries. Arbovirus, Japanese encephalitis, dengue, monoclonal antibody, neutralization test, Japanese encephalitis vaccine, vaccinia, Batai virus, Kasba virus, chikungunya virus, RA 1.