The primary goal of the disinfection process in drinking water treatment is the inactivation of microbial pathogens, which serve as the etiological agents of waterborne disease. The disinfection of water to be used for public consumption was first initiated in the early part of the century. There have been few developments in the area of public health which have been more effective in controlling the spread of infectious diseases. While other unit processes may dramatically reduce the number of microorganisms, disinfection serves as the final and in some cases the only barrier to the entry of microbial pathogens into the finished product water. Studies dealing with the disinfection process in drinking water treatment are an integral part of the research efforts of the U.S. Environmental Protection Agency (U.S. EPA). The manuscript summarizes recent research regarding the inactivation of microbial agents by a variety of chemical disinfectants.