The substitution of diethylene glycol for glycerin as a hygroscopic agent in industry makes it desirable to compare the toxicity of these two chemicals. Both have high boiling points, 245 and 290 C., respectively. Hence, small amounts may possibly pass unchanged with smoke from a cigaret into the body in addition to anything absorbed from the moist end of the cigaret in the mouth. In view of the rather high toxicity of the related ethylene glycol and because of the use of propylene glycol as a solvent for iodobismitol, it was thought desirable also to include a rough comparison between commercial samples of diethylene glycol and these two related chemicals.1 Recent exhaustive studies2have shown that glycerin may constitute a large proportion of the food of rats over long periods and that smaller amounts may be added to adequate diets of growing dogs and of man without apparent