Roma-BZCAT a multifrequency blazar catalogue

We present a new catalogue of blazars based on multi-frequency surveys and on an extensive review of the literature. It is useful for the identification of the extragalactic sources that will be detected by present and future experiments for X and gamma -ray astronomy, like Swift, AGILE, GLAST and SIMBOL-X. An electronic version is available from the ASI Science Data Center web site at http //www.asdc.asi.it/bzcat. The catalog presently includes objects between R.A.= 0h and 16h; the full sky is expected to be available by the end of 2007.