The Arizona Bureau of Mines has received so many requests for information about vanadium and Arizona deposits of ores of this metal that the stock of Bulletin No. 18, Vanadium, has been exhausted. In preparing this revision of the bulletin issued in 1916, that work has been completely rewritten and, so far as possible, brought up to date. The bulletin herewith offered is admittedly nothing but a compilation of facts already published, and no attempt has been made to make it an exhaustive treatise on the subject of vanadium. It is believed, however, that the data ordinarily sought by prospectors are herein presented, and it is hoped that the dissemination of this in formation will stimulate vanadium mining in Arizona. 23 p.