GenomePixelizer is a visualization tool that generates custom images of the physical or genetic positions of specified sets of genes in whole genomes or parts of genomes. Multiple sets of genes can be shown simultaneously with user-defined characteristics displayed. It allows the analysis of duplication events within and between species based on sequence similarities. The program is written in Tcl/Tk and works on any platform that supports the Tcl/Tk toolkit. GenomePixelizer generates HTML ImageMap tags for each gene in the image allowing links to databases. Images can be saved and presented on web pages.