intermediates in the biosynthesis of doublestranded ribonucleic acids of bacteriophage phi 6 pseudomonas phaseolicola infected with bacteriophage phi 6 synthesized all three viral doublestranded rna segments three singlestranded rnas and three replicative intermediatelike rnas in the presence of rifampin the singlestranded rna intermediates sedimented and electrophoresed along with melted viral doublestranded rna annealed with melted viral doublestranded rna and were transient in nature the relative amounts of the singlestranded rna intermediates varied during the infection cycle and were altered in the presence of chloramphenicol the replicative intermediatelike rnas sedimented faster than doublestranded rna failed to enter 25 polyacrylamide gels eluted with doublestranded rna from a cf11 cellulose column were precipitated with singlestranded rna in 2 m lic1 and yielded three genomesize pieces of doublestranded rna upon digestion with rnase these results are consistent with the hypothesis that complementary strands of the phi 6 doublestranded rnas are synthesized asynchronously during the infection cycle