The multistranded and double-stranded RNAs synthesized in HeLa cells infected with rhinovirus in the presence and in the absence of actinomycin D have been characterized by polyacrylamide gel electrophoresis and hybridization studies. The replicative form is only found in infected cells treated with actinomycin D, whereas the replicative intermediate is found in both the presence and the absence of the drug. The significance of these results is discussed.