The paper presents the history of the EPA wastewater disinfection research program from the early 1970's until it culminated with the publication of the Process Design Manual in September 1986. The program was elevated to the highest Agency research priority in 1976 with the infusion of over $1 million additional funds to accelerate development of alternative technologies. Reasons given for this supplemental funding included the findings that chlorine was toxic to aquatic life in low concentrations and reacted with precursors to produce potentially hazardous halogenated organic compounds. A number of projects were funded and each briefly discussed in the paper. Alternative technologies that became fully developed include ozone and ultraviolet light. Finally, the design manual, its organization and purpose, the project team, and the four years of hard work leading up to final publication are discussed.