The complete article is available as a provisional PDF. The fully formatted PDF and HTML versions are in production.We present GENECODIS, a web-based tool that integrates different sources of information to search for annotations that frequently co-occur in a set of genes and rank them by their statistical significance. The analysis of concurrent annotations provides significant information for the biological interpretation of high-throughput experiments and may outperform the results of standard methods for the functional analysis of gene lists. GENECODIS is publicly available at http://genecodis.dacya.ucm.es/Peer reviewed