We have examined the most favorable conditions for the agarose gel electrophoretic separation of RNA from several C-type RNA viruses. The influence of such factors as agarose concentration, temperature of gelation and the temperature and duration of electrophoresis were investigated. In contrast to polyacrylamide-agarose gel electrophoresis (PAGE), the resolving powers of agarose gels were not affected by the gelation temperature or the temperature of electrophoresis. The molecular weight values obtained for different viral RNA's were reproducible and did not differ significantly from those obtained using PAGE. Agarose gels have the added advantages of being easy to prepare and are non-toxic.