This report concerns a descriptive study undertaken in 1982-1983 as part of the Second International Science Study (SISS) under the auspices of the International Association for the Evaluation of Educational Achievement (IEA) for the purpose of examining key elements of K-12 science instruction in the United States. Special attention was directed toward identifying the nature of curricula planned in science for grades 5, 9, and 12 in order to develop valid items for the international testing program employed in SISS. An empirical study was designed to measure the relative emphasis given in curricula to science content and relevant cognitive, affective, and psychomotor objectives for grades 5, 9, and 12. Curricula grids were examined in the traditional science domains, in applied/integrated science areas, and for science processes, skills, and attitudes. Information reported in this publication includes: (1) introductory statements (discussing science education in the United States); (2) study procedures (explaining study methodology and data analysis); (3) survey results (presenting and interpreting the data); and (4) science curriculum case study (discussing findings on aims, objectives, curriculum development and content, teacher education, science teaching and associated topics). A 50-item bibliography is appended. (ML)