Poly(C, G) random copolymer templates direct the oligomerization of 2-Me-ImpG and 2-MeImpC, resulting in the production of a variety of oligo(G, C)s. The efficiency of monomer incorporation into newly synthesized oligomers is greater for 2-MeImpG than for 2-MeImpC, and decreases for both monomers as the guanine content of the template increases. The relatively low efficiency of oligomerization on guanine-rich templates is largely a consequence of intra- and intermolecular template self-structure. The problem of template self-structure is clearly a major obstacle to the development of a system of self-replicating polynucleotides. The distribution of oligomeric products can be characterized in detail using high-pressure liquid chromatography on an RPC-5 column. Oligomers are separated on the basis of chain length, base composition and phosphodiester-linkage isomerism. Oligomers up to about the 12-mer, with base composition Gn, Gn-1C and Gn-2C2, have been identified. The 3' to 5' regiospecificity of the products is high, particularly for oligomers with base composition Gn.