Hi, Try: #!/bin/perl -w > use Bio::SeqIO; > > $in = Bio::SeqIO->new ( -file => "xp_4.ace", -format => 'ace'); > $out = Bio::SeqIO->new (-file => ">xp.phd", -format => 'phd'); > while( $seq = $in->next_seq()) > { > $out->write_seq($seq); > } > This is covered in the SeqIO HOWTO <http://www.bioperl.org/wiki/HOWTO:SeqIO> . Dave