The uses, physical properties, chemical properties and health effects of exposure to 2-ethyl-2-hydroxymethyl-1,3-propanediol (77996) (trimethylolpropane) were reviewed as a basis for the development of occupational health standards by NIOSH and the Swedish National Institute of Occupational Health (NIOH). Trimethylolpropane has been used in the production of polyurethanes, polyester resins, alkyd coatings and acrylates. It has been found in photocurable coatings, paints, varnishes and dental sealants. Animal testing revealed low levels of toxicity by oral, inhalation and dermal exposure. The oral median lethal dose (LD50) in rats was about 14 grams per kilogram. Signs of acute intoxication included depression of the central nervous system and damage to the liver and kidneys. The dermal LD50 in rabbits was greater than 10 grams/kilogram. Mild irritative dermal effects have been noted in animals, but no convincing evidence of irritation has been found in humans. Epidemiological studies or case reports of workers exposed have not been found. No studies on carcinogenicity were available. Limited in-vitro studies did not show any signs of genotoxicity.