Because professional involvement in curriculum development is now commonplace in U.S. schools, it is imperative to consider the participants, their curriculum planning views, and the relationship of these views to the planning process. This paper describes a three-year study to determine whether the initial predispositions of participating teachers and principals were changed as a result of their active involvement in the collaborative curriculum planning process in a large Midwestern suburban school district consisting of 15,000 students and 750 teachers. The first year of the project (Phase 1) concentrated on defining the project's expectations, documenting the current district curriculum, and planning development activities. Phase 2 focused on developing new curricular components and revision recommendations for each content area. A curriculum system was also developed for implementing, maintaining, and evaluating the new content areas. Phase 3 involved implementing the new curricula in the four content areas (art, guidance, computers, and science) identified as needing immediate revision during the second phase. During all three phases, committees comprised of principals and teachers collaborated on various tasks. Findings show that teachers and principals involved in a broad-based curriculum planning process can reach consensus about curriculum uses. Furthermore, the more opportunities for curriculum planning of any sort, the more favorably teachers will view curriculum work. Several additional insights about participants are also summarized. Included are two tables containing data from the three phases of the curriculum planning project and instruments administered, respectively. (MLH)