WALTER J. MCCOY, THEN DIRECTOR OF RESEARCH for Lehigh Portland Cement Company, wrote the first version of this chapter for ASTM STP 169. For ASTM STP 169A, Mr. McCoy revised his chapter and added information on typical municipal water analyses, tolerable concentrations of impurities, the effects of sugar in mixing water, and the effects of water hardness on concrete air content. He also added several new references. For ASTM STP 169B, Mr. McCoy, then Director of Cement Technology for Master Builders, made only minor changes to the ASTM STP 169A version of the chapter. This current version is essentially Mr. McCoy's (now deceased) chapter with limited updating. There has been very little new technology published regarding mixing and curing water for concrete. The ASTM STP 169D edition as prepared does, however, reflect recent standards developments promulgated by ASTM Subcommittee C09.40 and Committee C09.