This document is the final report to develop a new elementary science curriculum. It contains information related only to the development phase of the Conceptually Oriented Program in Elementary Science (COPES) and was written for an audience that includes all who are interested in curriculum development as it was experienced in this project. The ultimate goal of the COPES program is to develop understanding of the nature of matter at various levels of sophistication. Five conceptual schemes were chosen for the curriculum: (1) The Structural Units of the Universe, (2) Interaction and Change, (3) The Conservation of Energy, (4) The Degradation of Energy, and (5) The Statistical View of Nature. These five conceptual schemes are interwoven in a logical hierarchy with all five being developed concurrently. Positioning of a concept within a particular scheme was determined on the following bases: its contribution as an introductory idea, its suitability for active exploration at a given age level, and its relative sophistication as a component of the scheme. The parts of the report are: Introduction, An Overview of COPES, the COPES Learning Activities and Assessments, Problems, Research Studies Dealing with COPES Materials, and The Future of COPES. (PEB)