Analyses of the 3' end sequences of the small, S, and large, L, RNA species of lymphocytic choriomeningitis (LCM) virus isolates ARM and WE, and DNA clones of LCM-WE, have shown that there are extensive RNA sequence homologies between the 3' ends of the two RNA species of both LCM strains. Limited sequence data of DNA clones representing the LCM-WE L RNA species indicate that a gene product (presumably the minor 200 kdalton virion protein) is coded in a viral-complementary mRNA species. Sequence analyses of LCM-WE S DNA clones indicate that approximately 50% of the 2040 nucleotides representing the 3' half of the viral RNA species (and its encoded 558 amino acid gene product) are identical in type and position to those of Pichinde arenavirus (Auperin, D., et al. (1984a), Virology 134, 208-219). For Pichinde virus, it has been shown that the 3' proximal gene product (the nucleoprotein, N) is translated from a subgenomic, viral-complementary mRNA (Auperin et al., 1984a). Data have recently been obtained (Auperin, D., et al. (1984b) J. Virol., in press) that indicate that the Pichinde glycoprotein precursor, GPC, is coded in a viral-sense subgenomic mRNA species corresponding to the 5' half of the S RNA. The nucleotide sequence that immediately follows the N coding region of both LCM-WE and Pichinde viruses can be arranged in a hairpin configuration. In view of this, and if, like Pichinde virus, LCM has an ambisense S RNA coding strategy, then it is probable that the intergenic hairpins function as transcription terminators for the N and GPC mRNA species of both viruses.