Disruption of purified lymphocytic choriomeningitis (LCM) virus with Nonidet P-40 in 0.5 M KCl followed by sucrose gradient centrifugation in 0.3 M KCl led to the isolation of two viral nucleoproteins (RNPs) as well as 40S and 60S ribosomal subunits. The largest viral RNP sedimented heterogenously at 123S to 148S and was associated with 23S and 31S viral RNA. The other viral RNP sedimented at 83S and was associated with 23S viral RNA. The buoyant density in CsCl was determined to be 1.32 g/cm3 for the viral RNP. Densities of 1.52 and 1.60 g/cm3 were determined for the 40S and 60S subunits, similar to those of the BHK-21 cells subunits dissociated by 0.5 M KCl. The viral RNPs were partly sensitive to RNase.