n 2006, for the first time, science will be the major focus of the PISA assessment of 15-year-olds. A major innovation in PISA 2006 is that many of the science units contain one or two items designed to assess students’ attitudes towards science – in particular, their interest in learning about science and their support for scientific enquiry. A second major innovation is that some of the items assess students’ knowledge about science – that is, their knowledge of scientific methodology. This paper presents some field trial results that shed light on what science students want to learn, and how their knowledge about science compares with their knowledge of science (biology, chemistry, physics, Earth and space science).