The Wide Field X-ray Telescope (WFXT) will provide tens of millions of AGN, with more than 4x10^5 expected at z>3. Here we review the issues present in the identification of (large) samples of faint and high-redshift X-ray sources, and describe a statistical, powerful tool that can be applied to WFXT catalogs. The depth of associated optical and near infrared catalogs, needed for a reliable and as much complete as possible identification, are also discussed, along with the combined synergies with existing or planned facilities ; Comment: 6 pages, proceedings of "The Wide Field X-ray Telescope Workshop", held in Bologna, Italy, Nov. 25-26 2009. To appear in Memorie della Società Astronomica Italiana 2010 (arXiv:1010.5889) "