The available archive of sequence databases compiled from whole genome projects and budding proteomics efforts have enabled us to develop VIRTUAL2D, an interactive system for the assembly of virtual protein expression maps computed on the basis of theoretical isoelectric focusing point, molecular weight, tissue specificity and relative abundance for any set of proteins currently catalogued. This tool will assist in the preliminary, albeit putative, prediction of the identity and location of unknown and/or low abundance proteins in experimentally derived two-dimensional polyacrylamide gel electrophoresis maps.