This article introduces how the human chromosome X-centric proteome project is carried out by the Japan Chromosome X Project Consortium. The inactivation of one of two chromosomes in female mammals and accumulation of genes related to neural/immune systems/tumor/testis are characteristic of chromosome X. In this Chromosome X Project, information on proteins translated from genes on chromosome X is collected by both mass spectrometry- and antibody-based proteomics. Information on the following resources is also provided: antibodies to proteins translated and full-length cDNAs transcripted from the chromosome X genes for recombinant proteins. The consortium aims to provide the following tools to search useful antibodies in the literature (Antibody Ranker), to find gene expression sites in microarray databases (Transcript Localizer) and to do advanced MRM analysis (information-based MRM).