The present book. Nucleic Acids Technologies describes latest applications of oligonucleotides and is composed of four chapters. In chapter - 1 Perspective in Deoxyribonucleic Acid Based Drugs, studies on Antisense oligonucleotide, Sense Oligonucleotides ( The decoy), Triplex Forming Oligonucleotides, Deoxyribozyme or DNA Enzymes and Aptamers are described. Perspective in Ribonucleic Acids Based Drugs deals with Ribozyme and RNAi are described in chapter- 2. Chapter-3 describes Diagnostic Applications of DNA Probes including Non-radioactive nucleic acid probes for the diagnosis of virus infection. DNA Chip Technology and its applications are described chapter -4.