[en] For the benefit of the National Environmental Policy Plan that will be published in 2001, the Netherlands Bureau for Economic Policy Analysis analysed four persistent environmental problems. These problems are the environmental effects of the manure surplus in the agricultural sector; the climate problem; the acidification by traffic and the air traffic noise around the airport Schiphol. This study not only looks ahead, but also looks back on 30 years of environmental policy. From a welfare economic perspective an analysis is made of the efficiency and effectiveness of that policy. Several questions are answered,e.g.: how could the manure problem of such a small sector as the livestock breeding persist for so many years?; how effective were the agreements with the industry and other sectors on energy efficiency improvement?; what made the acidification policy directed on traffic so successful?; why is the noise production of air traffic still a problem whereas the number of seriously bothered houses is decreased? The answers on these questions provide information which can be useful for the formulation of the future environmental policy. This information refers to the conditions for formulating adequate policy goals, the relation between those goals and policy instruments and the differences between direct versus indirect steering. This report also gives some points of interest for tackling complex international environmental problems. refs