The deoxyoctanucleotide (5′‐3′)d(A‐A‐G‐G‐A‐G‐G‐T), which is complementary to the 3′ end of 16‐S RNA, inhibits the formation of the complex between the 30‐S subunit and MS2 RNA described in the preceding paper. If the complex is preformed, the octanucleotide cannot prevent entry of the complex into the ribosome cycle upon supplementation with the components for protein synthesis. The subunit · MS2‐RNA complex is unable to bind the octanucleotide. It is concluded that in the subunit · phage‐RNA initiation precursor the 16‐S terminus is base‐paired with a complementary MS2 RNA sequence. Edeine, aurintricarboxylic acid and antibodies against ribosomal protein S1 prevent the association of phage RNA with 30‐S subunits. These compounds do not, however, inhibit the binding of (5′‐3′)d(A‐A‐G‐G‐A‐G‐G‐T) to 30‐S subunits. It is concluded that the formation of the complex between MS2 RNA and 30‐S subunits does not depend solely on the Shine and Dalgarno base‐pairing reaction.