The RPSP is a fast web service for detection of signal peptides in proteins. The method uses neural networks trained on known signal peptides from the Swiss-Prot protein database. The web server works either on prokaryotic and eukaryotic proteins or without specifying an organism type. The accuracy of the web server is similar to other available computational prediction web services, yet because of its speed and portability the method can be easily applied to whole proteomes. The RPSP web server is available at http://rpsp.bioinfo.pl. (C) 2007 Elsevier Ltd. All rights reserved.