Washington University BLAST (WU BLAST) version 2.0 is a powerful software package for gene and protein identification, using sensitive, selective and rapid similarity searches of protein and nucleotide sequence databases. WU BLAST 2.0 builds upon WU BLAST 1.4, which in turn was based on the public domain NCBI BLAST version 1.4. While NCBI BLAST and WU BLAST 1.4 are in the public domain, WU BLAST 2.0 contains significant new features and extended capabilities, the development of which began in late 1994, at Washington University in Saint Louis. First released in May 1996, or more than a year ahead of the NCBI, WU BLAST 2.0 is the original gapped BLAST with statistics and is known for setting higher standards for sensitivity, speed, correctness and accuracy, scalability and reliability than competing programs and implementations. WU BLAST is neither a re-hashed nor "Mac-ified" version of NCBI BLAST, although WU BLAST in many ways is easier to use. WU BLAST essentially shares no code with NCBI BLAST, except for portions that both packages derived from ungapped NCBI BLAST 1.4. WWW: http://blast.wustl.edu