DNA synthesis can be achieved by using O‐selective methods for internucleotide bond formation. This greatly simplifies the synthesis of oligodeoxyribonucleotides by eliminating the need for nucleobase protection and deprotection steps. This unit describes strategies that can be used for DNA synthesis without base protection. The discussion includes synthesis of phosphoramidite and H‐phosphonate monomers, solid‐phase assembly by the phosphoramidite and H‐phosphonate methods, and future prospects for DNA synthesis using N‐unprotected approaches.