The first synthesis of 5’-dithiophosphoryl deoxyoligonucleotides is reported. These oligomers are prepared by reacting O-(9-fluorenemethyl) H-phosphonothioate with an appropriately protected deoxyoligonucleotide and then oxidizing phosphorus with elementary sulfur. By using S-35-sulfur, a long-lived radioactive isotope that is useful for monitoring biological and biochemical experiments can be introduced into deoxyoligonucleotides. 5’-Dithiophosphoryl deoxyoligonucleotides are stable toward alkaline phosphatase and do not serve as substrates for T4-polynucleotide ligase. These oligomers undergo oxidative phosphoryl disulfide formation to yield dimers via an intermolecular reaction or with cysteine to generate an amino acid-deoxyoligonucleotide joined through the 5’-dithiophosphoryl moiety and the cysteine sulfhydryl function.