SeaView is a multiplatform, graphical user interface for multiple sequence alignment and molecular phylogeny. Important features are: 1) SeaView reads and writes various file formats (NEXUS, MSF, CLUSTAL, FASTA, PHYLIP, MASE, Newick) of DNA and protein sequences and of phylogenetic trees. 2) SeaView drives programs muscle or Clustal Omega (clustalo) for multiple sequence alignment, and also allows to use any external alignment algorithm able to read and write FASTA-formatted files. 3) Seaview drives the Gblocks program to select blocks of evolutionarily conserved sites. 4) SeaView computes phylogenetic trees by a) parsimony, using PHYLIP's dnapars/protpars algorithm b) distance, with NJ or BioNJ algorithms on a variety of evolutionary distances, c) maximum likelihood, driving program PhyML 3.1. 5) SeaView prints and draws phylogenetic trees on screen, SVG, PDF or PostScript files. 6) SeaView allows to download sequences from EMBL/GenBank/UniProt using the Internet. For details and citation: Gouy M., Guindon S. & Gascuel O. (2010) SeaView version 4 : a multiplatform graphical user interface for sequence alignment and phylogenetic tree building. Molecular Biology and Evolution 27(2):221-224.