Oryzomine rodents in the southeastern United States, Panama, and southern South America are natural hosts of 6 of the 13 viruses known to cause hantavirus pulmonary syndrome. The purpose of this study was to extend our knowledge of the geographical distribution and genetic diversity of the hantaviruses associated with oryzomine rodents in South America. An infectious hantavirus was isolated from two fulvous pygmy rice rats captured in western Venezuela. Analyses of complete nucleocapsid protein and glycoprotein precursor sequences indicated that the isolates are strains of a novel hantavirus (proposed name "Maporal") which is phylogenetically most closely related to the viruses known to cause hantavirus pulmonary syndrome in southern South America.