The iProClass database provides an integrated view of protein information (Huang et al., 2003) and serves as a bioinformatics framework for data integration and associative analysis of proteins (Wu et al., 2004). iProClass presents value-added descriptions of all proteins in UniProtKB and contains comprehensive, up-to-date protein information derived from over 90 biological databases. Rich links to the underlying sources are provided with source attribution, hypertext links, and extracted summary information. The source databases include those of protein sequence, family, function, pathway, protein-protein interaction, complex, post-translational modification, protein expression, structure and structural classification, gene and genome, gene expression,