In 2001, the U.S. Global Change Research Program produced the report A Plan for a New Science Initiative on the Global Water Cycle. This report was designed to represent a research strategy and scientific plan for investigating the global water cycle, and its interactions with climate and for developing an enhanced understanding of the fundamental processes that govern the availability and biogeochemistry of water resources. The USGCRP managers are currently considering how to move forward with implementation of this ambitious, broad, and potentially very fruitful plan on an interagency basis, and it requested that the National Research Council (NRC) advise them in this regard. This report, Review of USGCRP Plan for a New Science Initiative on the Global Water Cycle, provides comments on the water cycle science plan as related to its recommended scientific initiatives and goals, and it provides comments on the usefulness of the water cycle science plan to the USGCRP agencies in developing a coordinated global water cycle implementation plan.