The application of the systemic insecticides, Bayer 19639, Thimet and Am. Cyanamid 12008, on established stands of alfalfa was tested in granulated form for protection against the spotted alfalfa aphid, Therioaphis maculata (Buckton). Bayer 19639 at 1 pound of the active ingredient per acre was more effective than Thimet at the same rate during the “explosive” and relatively static high point of the infestation. Both materials were effective during the waning period of the population cycle in reducing the numbers of aphids to a non-economic level. Am. Cyanamid 12008 was ineffective in controlling the spotted alfalfa aphid when applied in a granulated form to established stands.