Accurate reactive chemicals data form the cornerstone of procedures used to assess the hazards associated with commercial chemical production and use. Since 1967, the ASTM E27 Committee on the Hazard Potential of Chemicals has issued numerous, widely used consensus standards dealing with diverse testing and predictive procedures used to obtain relevant chemical hazard properties. The decision to issue a standard rests solely with the membership, which consists of representatives from industry, government, consulting firms, and instrument suppliers. Consequently, the procedures are automatically relevant, timely, and widely applicable. The purpose of this paper is to highlight some of the widely used standards, complemented with hypothetical but relevant examples describing the testing strategy, interpretation, and application of the results. A further goal of this paper is to encourage participation in the standards development process. The paper is published in two parts. The first part deals with the E27 standards pertaining to thermodynamics, thermal stability, and chemical compatibility. The second part, to be publisbed in the next issue of this journal, focuses on the flammability, ignitability, and explosibility of fuel/air mixtures. (C) 2004 American Institute of Chemical Engineers Process.