The focus of this paper is on the earlier, recent and future developments in closing the water circuits in pulp and paper production. During the 1960s the U.S. pulp and paper industry was in its environmental infancy concentrating mainly on removal of settleable solids and initiating river assimilative capacity studies. The 1970s began with environmental legislation having enforceable powers to achieve primary and secondary (biological) treatment which was fundamentally fulfilled during the 1980s. The late 1980s and early 1990s opened with toxicity becoming the major environmental issue as measured mainly by absorbable organic halogens (AOX) and dioxins. This paper identifies progress and key technological developments towards furthering stringent environmental enhancement and provides additional knowledge requirements leading into the next century.