We present a method to predict cis-acting elements by detecting over-represented motifs in promoters of a set of coregulated genes (single-genome, multigenes approach). The method has been used successfully to detect regulating elements in bacteria and yeast. It can be used with higher organisms as well, but with a loss in reliability of the predictions. A web interface is available at the Regulatory Sequence Analysis Tools site (http://rsat.scmbb.ulb.ac.be/rsat/).