Radiolabeled Delnav® (2,3-p-dioxanedithiol S,S-bis (O, O- diethyl phosphorodithioate)) was applied to steers dermally and orally. Analyses of blood, urine, and feces indicated that the insecticide was rapidly metabolized and excreted. After 7 days both animals showed only trace amounts of radioactivity in the urine and feces, but the elimination of 20.4% of the dermal treatment indicates efficient absorption of the insecticide in comparison with other organophosphorus insecticides. The presence of three major hydrolysis products in the urine of both animals indicates a cleavage of Delnav at the P≁S+C as well as the P≁S—C bond, with oxidation before or after hydrolysis.