The National Curriculum for Science (NCS) introduced to schools in England and Wales in 1989 contained an earth science component that was new to many secondary science teachers. Ten years after this introduction, a survey was undertaken to test teacher perception of the effectiveness of their teaching in this subject area that was new to them., and to identify factors that might affect this effectiveness. The information gained has been used in reviewing possible curriculum changes and in developing professional development strategies that would improve the effectiveness of NCS earth science teaching. The data collected from science teachers who are currently teaching this earth science component revealed that their background knowledge of earth science from their own education was generally poor, even though most of them considered their knowledge to be "moderate." The teachers indicated that the achievement of their pupils in earth science is "moderate." while reports on national testing show it is poor. They reported that their main sources of earth science knowledge and understanding were science textbooks written for 11- to 16-year-old pupils (with their small earth science content of variable quality) and science colleagues (who often have poor earth science backgrounds too). Most teachers indicated that they needed more support in this area. Overall, the data indicated that while teachers consider their teaching in this area to be "moderate," other evidence suggests it is poor. If this situation is not to continue it should be addressed. In the longer term the emphasis on the earth science content of the National Science Curriculum could be changed (either enhanced or reduced) within larger scale curriculum changes. Until such curriculum change takes place, effective methods of professional development should be instituted so that teachers have a much improved basis on which to build their earth science teaching. Similar measures would be necessary in other countries and situations in which new curriculum material is introduced through a National Curriculum. (C) 2001 John Wiley & Sons, Inc. Sci Ed 85:636-664. 2001.