The Federal Water Pollution Control Act of 1956, as amended expresses the intent of the Congress that the states have primary responsibility for the abatement, control, and prevention of water pollution. The Federal role under the act is essentially to back up the States, that is, to initiate enforcement action when a state fails to act or when a state requests such action. This review is concerned primarily with the effectiveness of federal and state enforcement activities in ensuring that polluters constructed waste treatment facilities needed to attain the water quality standards established by the States and approved by the Federal Government. In general the review covers activities during the period 1957 through February 1971.