Pirital virus is a newly discovered South American member of the family Arenaviridae, We determined that the complete nucleotide sequence of the small genomic segment of Pirital virus is 3393 nt long, and encodes the viral nucleoprotein (N) and glycoprotein precursor (GPC) (561 aa and 509 as, respectively) in nonoverlapping open reading frames of opposite polarities. The N and GPC genes are separated by an intergenic region that is 80 nt long; the predicted secondary structure of this region includes a single hairpin stabilized by 11 G-C and 8 A-U base pairs. Independent analyses of N and GPC amino acid sequence data confirmed that Pirital virus is related to Pichinde virus and belongs to the lineage A of the New World (Tacaribe complex) arenaviruses, The analysis of genetic distances between Pirital virus and other arenaviruses confirmed that Pirital virus is a distinct species within the family Arenaviridae.