The effects of an emulsified rotenone preparation (Chem Fish Regular) on water treatment and water quality were investigated. Use of this material is planned for fish eradication in the Dickinson Reservoir, the sole source of water for Dickinson, North Dakota. Experiments indicate that rotenone can be removed or detoxified and odor problems controlled by using active carbon. Odor due to decomposed fish can be controlled with moderate chlorine dosages. The effects of the rotenone treatment should be naturally dissipated within a weeks. It appears feasible to produce a potable water from one treated with such a rotenone preparation. The worst difficulties are attributable to the hydrocarbon solvents used in the preparation.