The primary objective of the drinking water industry is to produce safe, potable water for its consumers at the lowest possible cost. As the definition of acceptable quality changes via federal regulations, many communities are experiencing difficulty in meeting the objective. Of particular concern for some communities is the ability to meet the trihalomethane (THM) standard. Previous research indicates that the use of combined chlorine as an alternative to free chlorine disinfection is one way that a utility can meet the THM standard. Currently, the U.S. Environmental Protection Agency (EPA) is concerned about the practice of chloramination as a means of disinfection because of its lower bactericidal control characteristics, as well as the possible formation of unidentified by-products. Recent research performed at Thornton, Colorado, has indicated that these concerns are warranted and that the quality characteristics of a water disinfected with chloramines varies considerably with the method of formation of combined chlorine. (Copyright (c) 1984 Env. Impact and Health Effects.)