On occasion of the publication of a book (H. SAS, ed.) a discussion of the predictability of the response of eutrofied lakes on a reduced external phosphorus loading is presented. Whereas the OECD study examines the correlations between nutrient loading and indicators for eutrofication for groups of lakes, the book discusses the direction of the response on reduction of the phosphorus loading for individual lakes. Although this is a valuable analysis that can increase the insight in the mechanisms controlling lake responses, neither the OECD study nor this book yield sufficiently unquestioned data that can be used directly in a a management framework. The relationships between loading and inlake concentration and between phosphate concentration and chlorophyll are discussed in some detail.