Ribozymes, RNA molecules which cleave RNA in a sequence-specific manner, are a promising tool in the development of specific antiviral therapies. The viruses most susceptible to ribozymes may be those in which all aspects of the viral life cycle depend on RNA, with no DNA intermediate. Consequently, we have chosen as a model one such virus, the arenavirus lymphocytic choriomeningitis virus (LCMV), and have previously reported the design of specific anti-LCMV ribozymes (Z. Xing and J. L. Whitton, J. Virol. 66:1361-1369, 1992). Here we describe the establishment of several cell lines, each stably expressing an antiarenaviral ribozyme of different specificity. Expression of a single ribozyme leads to a reduction in LCMV RNA levels, and stimulation of ribozyme transcription amplifies the effect. Target site selection may be an important determinant of antiviral effectiveness, since the extent of the antiviral effect, measured by assay of viral RNA, varies with the specificity of the antiviral ribozyme expressed. Furthermore, infectious virus production is reduced approximately 100-fold. This effect is LCMV specific, as yield of a related arenavirus is not similarly curtailed. We are currently investigating the mechanism underlying the ribozyme-mediated antiviral effect.