The toxicity and carcinogenicity of 6 food additives, safrole; alginic acid; polyoxyethylene-(20)-sorbitan monostearate (Tween® 60); 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline (Santoquin®); 1,3,5-trimethyl-2,4,6-tris-(3,5-di-tert-butyl-4-hydroxybenzyl)benzene (Ionox® 330); 2,4-bis-(4-hydroxy-3,5-di-tert-butylphenoxy)-6-(n-octylthio)-1,3,5-triazine (RA-858) were tested by 4 consecutive subcutaneous injections in infant Swiss albino mice, aged 1, 7, 14, and 21 days. Doses of safrole, alginic acid, Tween 60, or Santoquin in excess of 1 mg on day 1 of life were acutely toxic; Ionox and RA-858 were nontoxic at doses of 10 mg. Surviving mice were sacrificed at 1 year. After a total dosage of 6.6 mg safrole, a low incidence of multiple pulmonary adenomas, 6%, and pulmonary adenocarcinomas, 10%, and a high incidence of hepatomas, 58%, developed in 31 male mice alive at weaning, in contrast with a zero incidence of multiple pulmonary adenomas and pulmonary adenocarcinomas, and a 5–6% incidence of hepatomas in uninjected and solvent-injected controls, based, respectively, on 36 and 78 males alive at weaning. In groups tested with alginic acid and RA-858, tumor incidences fell within control ranges; carcinogenicity data for Santoquin and Ionox were equivocal. These results confirm the practical utility of neonates for carcinogenicity testing in that remote tumors develop rapidly following restricted parenteral administration of relatively small quantites of test materials.