On the basis of the distance-dependence of DNA-templated reductive amination reactions and of recent findings of D. Lynn and co-workers, we developed DNA-templated polymerizations of synthetic peptide nucleic acid (PNA) aldehydes. The coupling reactions proceed in a highly efficient and sequence-specific manner, even in the presence of mixtures of PNA aldehydes of different sequence. Synthetic peptide nucleic acid polymers containing as many as 40 PNA units (representing 10 consecutive coupling reactions) were formed efficiently. The ease of preparing PNAs containing tailor-made functional groups together with these findings raises the possibility of evolving synthetic sequence-defined polymers by iterated cycles of translation, selection, PCR amplification, and diversification previously available only to biological macromolecules.