This proposal requests funds to enable U.S. scientists, particularly young investigators, postdoctoral fellows, and predoctoral students to attend the Fourth International Positive-Strand RNA Virus Symposium in Utrecht, The Netherlands, May 25-31, 1995. Symposium co-organizers are Margo A. Brinton, Georgia State University; Willy Spaan, University of Leiden; and Rob Goldbach, Agricultural University. The scientific program will be organized with the aid of a Program Committee. Eight Plenary sessions and one short talk session will contain talks on 3D-structure analysis of viruses and viral proteins; Viral entry mechanisms (receptors, penetration and uncoating); RNA expression, replication, transcription and recombination; RNA structure and RNA-protein interactions; Virus assembly; Interference with virus replication at the intracellular level; RNA virus evolution and emerging viruses; Strategies for control of virus diseases (transgenic crop, vaccine development and antivirals); and Pathogenesis (tropism, virulence and spread of virus infections). At least seven families of animal viruses, the majority of the plant viruses, one family of insect viruses and one family of bacteriophages are of this type. Diseases caused by these viruses are of medical, agricultural, and are positive strand RNA viruses. Diseases caused by these viruses are of medical, agricultural, and economic significance and include human encephalitis, poliomyelitis, heart disease, hepatitis, the common cold, gastroenteritis, hemorrhagic fever, and birth defects. Positive-strand RNA virus infections are often fatal in patients immunosuppressed because of cancer, transplantation, or AIDS. Previous International Positive-Strand RNA Virus Symposia were held in 1986, 1989, and 1992. Because of the broad-based international attendance of the symposium, the conference site alternates between the U.S.A. and Europe. All three of the previous meetings were extremely successful in achieving the goal of promoting discourse and scientific collaboration between animal, plant, and insect virus researchers.