Protein separation by two-dimensional gel electrophoresis is of central importance for proteomics. Upon combination with systematic protein identifications by mass spectrometry, large data sets are routinely generated in several proteome laboratories which can be used as "reference maps" for future analyses of analogous biochemical fractions. Here we present GelMap, a novel software tool for the building presentation and evaluation of proteomic reference maps. Variable frames are introduced in order to group proteins into functional categories on three levels or into categories according to differential abundance during comparative proteome analyses. The software is easy to handle as it only requires uploading two digital files to a web site. An additional file including detailed information on all proteins can be combined with the primary map. Two different gel-based projects are presented to illustrate the capacity of GelMap for proteome annotation and evaluation.