A new algorithmic approach to comparing 2D patterns of protein spots obtained by the 2D gel electrophoresis technique is presented. Both the matching of a local pattern vs. a full 2D gel image and the global matching between full images are discussed. Preset slope and length tolerances of pattern edges serve as matching criteria. The local matching algorithm relies on a data structure derived from the incremental Delaunay triangulation of a point set and a 2–step hashing technique. The approach for the global matching uses local matching for landmark settings, which in most previous algorithmic solutions has been done interactively by the user.