The use of chlorinated hydrocarbons, namely trichlorbenzene, ortho-dichlorbenzene, and mono-chlorbenzene is indicated for the control of aquatic vegetation in localized areas. Ortho-dichlorbenzene is best because it settles fast and does not impart any great amount of odor or taste to the water. These chemicals, which are relatively insoluble in and heavier than water, sink to the bottom and sterilize it for a period of time. Trichlorbenzene is least satisfactory as it disperses far past the limits of the area to which applied. It also imparts a disagreeable odor and taste to the water and fish. It is possible that trichlorbenzene, with an emulsifier added, might prove an effective fish poison.