RNA extracted from purified Pichinde virion preparations yields four major species, two of which appear to represent the viral genome while the other two appear to be cellular ribosomal 28S and 18S RNA. The molecular weights of these RNA species have been estimated by gel electrophoresis following denaturation by either methylmercury or glyoxal/dimethyl sulfoxide. The values determined by the two methods are in close agreement. The average molecular weights of L and S Pichinde viral RNA are 2.63 x 10(6) to 2.83 x 10(6) to 1.31 x 10(6), respectively.