This booklet consists of four papers by separate authors that show how the Dutch National Institute for Curriculum Development (SLO) tries to improve the quality of education through curriculum research and development. The first text, by Johan C. van Bruggen, provides a general introduction to SLO, showing how it generates curriculum knowledge among school practitioners through five principles and procedures. The second text, by Ivar Labordus, sets forth a hypothetical curriculum development strategy for a national system of comprehensive junior secondary education. The third paper, by Kerst Boersma, describes specific problems in an SLO project for science curriculum in junior secondary education. The fourth paper, by Eddy O.I. Jozefzoon, analyzes problems involved in evaluating the work of SLO. It reports on research projects that provide evidence of the actual effects of SLO projects. The second part of the booklet provides information about the educational system in the Netherlands, the SLO as part of the educational support structure, an overview of the curriculum development projects of the SLO, and a review of curriculum research projects. (TE)