A review of applications of chemically synthesized oligodeoxynucleotides to gene technology is given. At first the reader is briefly introduced to the methods of oligodeoxynucleotide synthesis. With selected examples the utilization of synthetic oligodeoxynucleotides is discussed in some detail for sequencing DNA and RNA, for the incorporation of base analogs and sequence specific mutations into nucleic acids of natural origin, for the isolation of specific nucleic acid sequences from biological sources, for the specific inhibition of virus reproduction, as linker molecules for gene cloning experiments and for the total synthesis of signal structures (regulatory sequences) and structural genes. The importance of synthetic oligodeoxynucleotides for molecular biology and gene technology especially is emphasized.