The NOAA Chemical Reactivity Worksheet (CRW) has provided a user-friendly, yet powerful method of qualitatively predicting reactive chemical hazards since its introduction in 1998, and has seen its use in spill response, storage management, and process safety for intentional chemistry. The CRW predicts reaction hazards based on a database of more than 6,000 common industrial chemicals, classified by major reactive groups, using 43 x 43 matrix of organic and inorganic reactive groups, modified from the earlier "'EPA method for determining the compatibility of hazardous mixtures." CRW output describes the hazards qualitatively; e.g., "spontaneous ignition of reactants or products due to reaction heat," or "combination liberates nonflammable, nontoxic gas and may cause pressurization. The CRW also provides summaries of properties and special hazards for many of the compounds in the database. CRW 2.0, a new, standalone version of the CRW is due to be released later this year. Earlier versions of the CRW had a limited set of references and limited information about specific reactions, and this information could only be found in each compound's chemical profile, increasing search time for assessing reaction specifics, and providing little information that could be used to mitigate the chance of false-positives-the CRW is designed to be conservative in its predictions, and will indicate an incompatibility even if only a few reactions are found between two functional groups. Version 2.0 improves the database based on an extensive literature survey of potentially hazardous reactions for representative members of all 43 listed functional groups, with primary literature references available for many of the hazards predicted, and many errors and omissions corrected. This article describes the methodology for the literature search, rationale for changes to the operation of the database,. extent of the new documentation, and the remaining design limitations of the product. (C) 2008 American Institute of Chemical Engineers Process Saf Prog 27: 212-218, 2008.