  We present a new catalogue of blazars based on multi-frequency surveys and on
an extensive review of the literature. Blazars are classified as BL Lacertae
objects, as flat spectrum radio quasars or as blazars of uncertain/transitional
type. Each object is identified by a root name, coded as BZB, BZQ and BZU for
these three subclasses respectively, and by its coordinates. This catalogue is
being built as a tool 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, Fermi-GLAST and Simbol-X. An electronic
version is available from the ASI Science Data Center web site at
http://www.asdc.asi.it/bzcat
