This invention relates to the synthesis of nucleic acid-encoded chemical libraries using common adaptor sequences. Nucleic acid strands coupled to chemical moieties may be contacted with identifier oligonucleotides comprising coding sequences encoding the chemical moieties and an adaptor oligonucleotides, such that the adaptor oligonucleotide hybridizes to both the nucleic acid strands and the identifier oligonucleotides to allow ligation of the identifier oligonucleotides to the nucleic acid strands. The adaptor oligonucleotide is then removed. Nucleic acid-encoded chemical libraries, and methods of producing or screening such libraries are provided.