THE OCCURRENCE of two deaths from an outbreak of thallotoxicosis involving four children who attended the same preschool nursery is herein reported. Although thallium was discovered in 1861 by Crookes,1 its toxicity was not recognized for some years. Initially thallium acetate was used internally to combat night sweats in tuberculous patients,2 and later it was employed for the treatment of ringworm infection of the scalp. In 1931 Lubin introduced thallium acetate in a depilatory cream, under the trade name of koremulu. Numerous cases of poisoning were reported from its use. Most poisonings, however, have occurred as a result of the internal use of thallium acetate as a depilatory in the treatment of ringworm in children. Thallium poisonings in industry also have been recorded. In 1920 thallous sulfate was introduced in Germany as a rodenticide under the trade name of zelio. The German literature3 contains reports of both