The oral chronic toxicity of diphenyl has been investigated by feeding this compound to rats for a period of two years and to monkeys for one year. Reproduction studies with rats fed diphenyl were carried out through three generations. The effect of diphenyl as the skin was studied by repeatedly applying the compound to the skin of rabbits over a period of six weeks. Storage studies of citrus fruit wrapped in diphenyl impregnated tissues were carried out to determine the amount of diphenyl absorbed into the peel and juice. An analytical chemical method was developed for the analysis of diphenyl in citrus peel and juice. The sensitivity and accuracy of this method was found to be plus or minus 1.0 microgram of diphenyl per gram of orange peel. Citrus fruit wrapped in diphenyl-impregnated tissues and stored for as long as eight weeks were found to contain 0.0 to 3.3 micrograms of diphenyl per milliliter of juice while the average concentration of diphenyl in citrus was less than 2 micrograms per milliliter of juice throughout the entire storage period.