Diethylene glycol (DEG) is an organic chemical that is used mostly as a chemical intermediate and has minor uses as a solvent or antifreeze in consumer products; these minor uses could result in potential human exposure. Potential short and long-term human exposures also occur from misuses. The considerable reporting of DEG misuses as a substitute for other solvents in drug manufacturing and summaries of important events in the history of DEG poisonings are reviewed. Given the potential for human exposure, the disposition and toxicity of DEG were examined, and a health assessment was performed. Toxicokinetics and metabolism studies are evaluated, along with a discussion on the renal toxicity mode of action in the rat. Additionally, in-depth assessments of the key animal research studies on the toxic effects of DEG from oral ingestion for various exposure time periods are presented with determination of NOAELs and LOAELs from the long-term exposure animal studies. These are applied in the derivation of a reference dose for a non-cancer endpoint from chronic exposure, resulting in a value of 0.3 mg DEG/kg bw.