Laboratory and field-cage studies were conducted in Texas in 1965 to evaluate treatments of the systemic insecticides, Azodrin (3-hydroxy-N-methyl-cis-crotonamide dimethyl phosphate), Bidrin (3-hydroxy-N, N dimethyl-cis-crotonamide dimethyl phosphate), American Cyanamid CL-47031 (cyclic ethylene (diethoxy-phosphinyl) dithioimidocarbonate) and Temik (2-methyl-2-(methylthio) propion-aldehyde O-(methylcarbamoyl) oxime), applied incorporated in lanolin to the stems of cotton plants against Heliothis zea (Boddie) and H. virescens (F.). Reductions in numbers of developing larvae of H. zea were substantial on individual plants the stems of which had been treated with Azodrin or CL-47031 and which were artificially infested with eggs. When first-instar larvae of H. zea or H. virescens were caged on plants 3, 7 or 14 days after stem treatment with 2.5, 5.0 or 100 mg. Azodrin, Bidrin or CL-47031 per plant, net mortalities ranged from 21 to 80 per cent after three days. The mortality of adults of H. zea provided with sucrose solutions containing 1 p.p.m. of the systemic insecticides indicated that Azodrin and Bidrin were about equally toxic and much more so than CL-47031 and Temik, and that of adults caged on individual plants in flower that had been treated with Azodrin or CL-47031 suggested that the moths may be killed by the systemic action of these insecticides translocated to the nectar. When adults of H. virescens were released on plants each treated with Azodrin at 25 or 30 mg. in large field cages, reductions in the numbers of eggs deposited, attributed to the effect on the moths of the insecticide in the nectar, and in the numbers of developing larvae, were substantial. Azodrin was the most consistently effective of the four insecticides evaluated.