The systemic insecticides Thimet®, (O,O-diethyl S-(ethylthio) methyl phosphorodithioate), Bayer 19639 (Di-Syston® = O,O-diethyl S-2-(ethylthio)ethyl phosphorodithioate), demeton thiol-isomer, (O,O-diethyl S-2-(ethylthio)ethyl phosphorothioatc) and demeton were evaluated in a series of field experiments for control of the cabbage aphid, Brevicoryne brassicae (L.), on cabbage in southern California. Seed-coat applications of both Bayer 19639 and Thimet on activated charcoal at the rate of 4 pounds of toxicant per 100 pounds of seed caused a reduction in plant stand. Moderate control of the green peach aphid, Myzus persicae (Sulz.), was obtained for as long as one month by this method. Granulated Bayer 19639 and Thimet applied to the seed furrow at the rate of about 1 pound of toxicant per acre gave control of the cabbage aphid for 2 months with no apparent reduction in the number of plants. Bayer 19639 applied at about the same rate as a spray to the seed furrow also gave aphid control for 2 months. Thimet and Bayer 19639 were applied as granules at the rate of ½, 1, and 2 pounds per acre to the transplant furrow. Bayer 19639 at the 1- and 2-pound dosages gave good control for at least 2 months under moderate population pressure. Thimet at similar dosages gave good initial kill but was not effective over as long a period. Both materials at one-half pound per acre gave early control but lost their effectiveness after about 1 month. Bayer 19639 applied as granules directly to aphidinfested foliage at dosages as low as one-fourth pound per acre gave good control in 5 days and was still effective 17 days after treatment. Thimet at similar concentrations was also effective. Bayer 19639 generally gave longer aphid control than Thimet. Residue studies indicate that Thimet and Bayer 19639 applied to the plants at time of transplanting, or soon thereafter, had dissipated almost entirely from the cabbage heads at harvest time. Samples also indicate that Thimet breaks down somewhat faster than Bayer 19639.