Canadian participation in the Second International Science Study (SISS) has both international and national aims. The international aims are identical with those of SISS and call for a description of science education policy and practice, student achievement testing, and the analysis of students' and teachers' attitudes to science and science teaching. The national aims relate to the diversity of science education in the ten provinces and two territories, each of which constitutes an independent educational authority. This part of the study will compare science curriculum policies with science curriculum practices, will examine the relationship of policy to practice, and will investigate relationships between the mandated and the achieved curriculum. The focus on the policy/practice interface leads to the study of a number of issues, in particular to a study of the nature of policy and of curriculum as presented in official documents, and to a study of teachers' perceptions of the curriculum. (Author)