This catalogue is an update of the previous versions; as in the previous editions no information about absorption lines of X-ray properties are given, but absolute magnitudes are given, assuming Ho=50km/s/Mpc and q_0_=0. In this edition the 20cm radio flux is listed when available, in place of the 11cm flux. The present edition of this catalogue contains the quasars with measured redshift known prior to January 1st, 2006. It contains 85221 quasars, 1122 BL Lac objects and 21737 active galaxies (including 9628 Seyfert 1s), almost doubling the number listed in the 11th edition. Lists of known lensed quasars (table2.dat) and double quasars (table3.dat) are also given here. Version history: (1) Veron-Cetty M.P., Veron P., 1984, ESO Scientific Report 1 (2) Veron-Cetty M.P., Veron P., 1985, ESO Scientific Report 4 (3) Veron-Cetty M.P., Veron P., 1987, ESO Scientific Report 5 (Catalogue <VII/93>) (4) Veron-Cetty M.P., Veron P., 1989, ESO Scientific Report 7 (Catalogue <VII/126>) (5) Veron-Cetty M.P., Veron P., 1991, ESO Scientific Report 10 (Catalogue <VII/146>) (6) Veron-Cetty M.P., Veron P., 1993, ESO Scientific Report 13 (Catalogue <VII/166>) (7) Veron-Cetty M.P., Veron P., 1996, ESO Scientific Report 17 (Catalogue <VII/188>) (8) Veron-Cetty M.P., Veron P., 1998, ESO Scientific Report 18 (Catalogue <VII/207>) (9) Veron-Cetty M.P., Veron P., 2000, ESO Scientific Report 19 (Catalogue <VII/215>) (10) Veron-Cetty M.P., Veron P., 2001, Astron. Astrophys. 374, 92 (Catalogue <VII/224>) (11) Veron-Cetty M.P., Veron P., 2003, Astron. Astrophys. 412, 399 (Catalogue <VII/235>)