Summary reports on toxicity tests of diphenyl oxide indicate that 0.2 g/kg bw suspended in 5 - 10% gum acacia solution and administered by gavage to cavies was not lethal, while 1.2 g/kg killed all test animals within 2 weeks post-administration. Nineteen doses of 0.1 g/kg fed (test species not identified) over a period of 29 days caused minor changes (not further described) in one liver lobe. Qualitative experiments involving dermal exposure indicated a single application of test chemical to the ear of the rabbit was non- irritating, while on the abdomen, edema, hyperemia, exfoliation and crustation were evident for 3 to 7 days. Six applications made over a period of 10 days produced exfoliation and necrosis on the ear, and hyperemia, exfoliation, and epithelial hyperplasia on the abdomen.