The large-scale and rapid identification and characterization of proteins, for example those separated on 2-D gels, represents a central step in the understanding of a proteome. Identification involves the matching of analytical data against protein databases in order to assign a protein as already known or to describe it as novel. Researchers can take advantage of the information contained in databases to predict a number of properties inherent to proteins of interest. The aspects of identification and of structural prediction are complementary and both required in the characterization process of a protein and, more generally, of a proteome. In that respect the development of the World-Wide Web (WWW) is changing the research of all life scientists and in particular of protein chemists and biomedical scientists. The WWW environment allows to search for information in continuously updated databases that are physically located anywhere in the world, to match experimental data with those stored in different and interconnecting databases, to interactively predict protein attributes using intelligent tools, to discuss results and problems with colleagues through newsgroups and other online forums, to share results and suggestions with people in charge of the databases and bioinformatics tools in order to improve the quality of the databases and the power of the tools.