The signal recognition particle database (SRPDB) is maintained at the University of Texas Health Science Center at Tyler, Texas, and organizes SRP-related information about SRP RNA, SRP proteins and the SRP receptor. SRPDB is accessible on the WWW at the URL http://psyche.uthct.edu/dbs/SRPDB/SRPDB.++ +html. A mirror site of the SRPDB is located in Europe at the University of Göteborg, Sweden (http://www.medkem. gu.se/dbs/SRPDB/SRPDB.html ). This release of SRPDB adds 10 new SRP RNA sequences (a total of 117 SRP RNAs), four protein SRP19 sequences (a total of 15), seven new SRP54 (ffh) sequences (a total of 52), and eight sequences of the SRP receptor alpha subunit (FtsY) (total of 36). Sequences are arranged in alphabetical and phylogenetic order and alignments are provided which highlight base paired and conserved regions. SPRDB also provides motifs to find new sequences, a brief introduction to SRP function in protein secretion, numerous SRP RNA secondary structure diagrams, 3-D SRP RNA models, and recently obtained crystal structure PDB coordinates of the human SRP54m domain.