This report uses the Core-Plus Mathematics Project (CPMP) as a case-study example of how new high school curricula have developed in the United States over the last decade since the publishing of the first NCTM Standards Documents (1989, 1991). Beginning with a description of both the curriculum itself and the rationale used to guide its development, the report highlights the associated research and evaluation results that have emerged in terms of students' achievement data on a variety of measures. The report concludes by documenting the growth of CPMP-related professional development activities that are an integral part of successful implementation of new curricula and then identifying and addressing four emerging issues associated with implementation. A consistent theme throughout is the notion that, in general, curriculum development is an ongoing process and specifically that those results highlighted in this report are used to inform a new revision of Core-Plus Mathematics currently underway. (Author)