PRINTS is a compendium of protein motif 'fingerprints' derived from the OWL composite sequence database. Fingerprints are groups of motifs within sequence alignments whose conserved nature allows them to be used as signatures of family membership. To date, 400 fingerprints have been constructed and stored in Prints, the size of which has doubled in the last year. The current version, 9.0, encodes approximately 2000 motifs, covering a range of globular and membrane proteins, modular polypeptides, and so on. Fingerprints inherently offer improved diagnostic reliability over single motif methods by virtue of the mutual context provided by motif neighbours. PRINTS thus provides a useful adjunct to the widely used PROSITE dictionary of patterns. The database is now accessible via the Database Browser on the UCL Bioinformatics server at http://www.biochem.ucl.ac.uk/bsm/dbbrowser .