In an effort to find alternatives to brine acidification for control of siliceous scale deposition in geothermal resource production facilities, a second series of laboratory screening tests with new organic inhibitors has been conducted. In the first series of tests, organic inhibitors, usually consisting of dispersants and phosphino-carboxylic acid mixtures, were examined for silica scale control activity [Gallup, D.L., 2002. Investigations of organic inhibitors for silica scale control in geothermal brines. Geothermics 31, 415-430]. The present study consisted of screening additional inhibitor formulations obtained from seven different manufacturers in a laboratory pressure reactor using a synthetic brine solution. Several of the organic inhibitors yielded promising scale deposition results. Similar to the initial series of tests, brine acidification always out-performed the organic inhibitors. Acid precursors also appear to be acceptable alternatives to strong acids as a means of limiting corrosion, transportation risks and safety/handling issues. (c) 2005 CNR. Published by Elsevier Ltd. All rights reserved.