SeaView reads and writes various file formats (NEXUS, MSF, CLUSTAL, FASTA, PHYLIP, MASE, Newick) of DNA and protein sequences and of phylogenetic trees. Alignments can be manually edited. It drives the programs Muscle or Clustal Omega for multiple sequence alignment, and also allows one to use any external alignment algorithm able to read and write FASTA-formatted files. It computes phylogenetic trees by parsimony using PHYLIP's dnapars/protpars algorithm, by distance with NJ or BioNJ algorithms on a variety of evolutionary distances, or by maximum likelihood using the program PhyML 3.0. SeaView draws phylogenetic trees on screen or PostScript files, and allows one to download sequences from EMBL/GenBank/UniProt using the Internet.