A novel solid-phase phosphoramidite based oligodeoxynucleotide two-step synthesis method has been developed. Keys to this method are replacement of the 5'-dimethoxytrityl blocking group with an aryloxycarbonyl and the use of N-dimethoxytrityl protection for the exocyclic amines of adenine and cytosine. With these modifications, coupling of each 2'-deoxynucleoside 3'-phosphoramidite to the growing oligodeoxynucleotide on the solid support can be followed by treatment with an aqueous mixture of peroxy anions buffered at pH 9.6. This reagent effectively removes the carbonate protecting group and simultaneously oxidizes the phosphite internucleotide linkage. As a consequence a new two-step synthesis cycle is possible. Oligodeoxynucleotides synthesized using this approach are identical to authentic samples when tested by a variety of analytical techniques.