This article addresses the issues involved in monitoring the teaching and learning of science in a changing world. It examines the development of cross-cultural studies of educational achievement, particularly in the field of science, including the theoretical basis of the studies and the models advanced and used in evaluation and more recently in the monitoring of change over time. In addition ten specific issues are identified for investigation into the critical problems facing learning and teaching of science across the world at the beginning of the twenty-first century with particular reference to the PISA studies being conducted by the Organisation for Economic Cooperation and Development. (Contains 6 figures.)