Summary: A Tcl/Tk-based application called GenoMap is described, a viewer for genome-wide map of microarray expression data within a circular bacterial genome. An interactive interface facilitates easy identification of the expressed region. This software is also used for drawing genome-wide quantitative data. Availability: The program is freely available to academic users as a Tcl/Tk source code at http://www.molbiol.saitama-u.ac.jp/~naoki/GenoMap/ Contact: naokisat@molbiol.saitama-u.ac.jp