Background information on ethylene-oxide (75218) (EO) is presented and plans for investigating facilities involved in the manufacture of EO are outlined. Physical and chemical properties of EO are given. The manufacture of EO by direct oxidation and by the chlorohydrin process is described. A list of EO manufacturers is included. The uses of EO are discussed. The acute and chronic effects of EO are summarized. Mutagenicity and carcinogenicity studies in animals are reviewed. The effects of EO on human skin are discussed. The instruments to be used in analyzing the atmosphere of EO manufacturing facilities are described. An analytical procedure, consisting of adsorption of EO on charcoal, desorption with carbon-disulfide, and analysis by gas chromatography, is presented step by step. Target facilities of the investigation are listed. The process of site selection is outlined. The type of information considered relevant in EO study, such as job functions, number of workers exposed, work histories of exposed workers, and raw materials used, is presented.