A summary of toxicity tests of diphenyl indicate it is 100% lethal at acute doses of 3 g/kg bw in rats, and repeated doses (20) of 0.1 g/kg was not toxic to the rabbit. A single dermal application of 5% solutions in 95% ethanol and olive oil caused no irritation to rabbit ears and repeated applications (20) to the abdomen caused only a slight reaction. Diphenyl oxide caused 100% lethality to cavies and rats at acute doses of 4.0 g/kg bw. Single dermal application of undiluted diphenyl oxide to rabbit ears produced a slight reaction, while neither 20% nor 5% solutions in olive oil caused irritation. Repeated (20) applicationsof the 20% and 5% olive oil solutions produced a slight reaction. Six applications of undiluted material produced a moderate reaction which healed quickly when treatment was discontinued. One abdominal application of undiluted material produced a moderate reaction, while a minimum of 9 applications of the 20% solution and 14 of the 5% solution caused similar reactions.