Executive Summary Perchloroethylene (PCE, or perc) has been the subject of close government and public scrutiny for more than 20 years. But government agencies in the U.S. and around the world have not agreed about the potential of environmental exposure to PCE to cause adverse health effects, including cancer, in humans. This report summarizes and evaluates the evidence behind these disparate views, and provides a balanced assessment of the possible risks of PCE based on the best available science.