OLIGO is a multi-functional program that searches for and selects oligonucleotides from a sequence file for polymerase chain reaction (PCR), DNA sequencing, site-directed mutagenesis, and various hybridization applications. It calculates hybridization temperature and secondary structure of oligonucleotides based on the nearest neighbor thermodynamic values. It is also a good tool for construction of synthetic genes, finding an appropriate sequencing primer among those already synthesized, finding and multiplexing consensus prmers and probes, and even finding potential restriction sites in a protein. The OLIGO software has been broadly accepted as the industry software standard for selecting and analyzing oligonucleotides for various molecular biology applications. The first commercial version of the software has been introduced in 1989.