This is the fourth and final volume reviewing EPA's Environmental Monitoring and Assessment Program (EMAP). After 4 years of review, the authoring committee retains its belief that EMAP's goals are laudable. However, because achieving the goals of this ambitious program will require that EMAP successfully meet the difficult scientific, practical, and management challenges, the committee continues to question whether and how well all these goals can be achieved. This final overall review reiterates that general assessment.