In 1958 and 1959 cattle were sprayed with 11 insecticides to control lone star ticks (Amblgmma americanum (L.). The considerable, variation in effectiveness of the standard, 0.5% toxaphene, at 1 week post treatment was dependent upon reinfestation pressure. One week after treatment 0.5% Co-Ral® was most effective, 0.5% toxaphene, 0.75% ronnel, and 0.5% malathion afforded equal protection, and 0.025% lindane was the least effective of these recommended sprays. Of the newer compounds tested, 0.15% Delnav® and 0.5% Sevin® afforded greater reductions than toxaphene; 0.5% Bayer 22408 was as effective as the standard; and dicapthon, Dipterex® and Ruelene® gave least reductions. None of the treatments were effective after 2 weeks. The chemical names of the compounds are Co-Ral (O-(3-chloro-4-methylumbelliferone) O,O-diethyl phosphorothioate), Delnav (2,3-p-dioxanedithiol S,S-bis(O,O-diethyl phosphorodithioate) (68% to 70% and related materials) Sevin (1-naphthyl methylcarbamate), Bayer 22408 (O,O-diethyl O-naphthalimido phosphorothioate), Dipterex (dimethyl 2,2,2-trichloro-1-hydroxyethylphosphonate), and Ruelene (4-tert-butyl-2-chlorophenl methyl methylphosphoramidate).