aStandards of swimming pool operation have been developed to prevent the spread of communicable diseases and to insure the safety and well-being of persons frequenting swimming pools. Of principal importance are the standards related to the bacterial quality of the water and the procedures for purification. Because of its simplicity of application, its economy of use, and its continuing, bactericidal action through the maintenance of residual levels, chlorine has been and is being used extensively to control the quality of swimming pool water High-free chlorine residuals in swimming pool water have proved so satisfactory in maintaining the sanitary quality of the water that less emphasis will need to be placed on bacterial standards if accurate titrations of the residuals are routinely carried out, say the reporters of this research.