Results of four experiments on 5.5-acre Deer Island Lake demonstrated that selective poisoning was a practical method for reducing the gizzard shad population. Past haul seine efforts had effected only a temporary reduction in this lake. A concentration of 0.04 p.p.m. of 5 percent emulsified rotenone killed very few gizzard shad. A 0.1 p.p.m. concentration resulted in a conservatively calculated kill of 4,651 pounds or 846 pounds per surface acre. An application of 0.15 p.p.m. concentration killed larger shad as well as a few bass. A subsequent application of 0.1 p.p.m. concentration produced a large unexplained kill of bass.