9600023 Simon The Mathematics Teacher Development (MTD) Project is designed to conduct detailed study of the development or preservice and inservice mathematics teachers as the develop form traditional conceptions of mathematics, learning, teaching, and classroom practice towards conceptions that are consistent with current mathematics education reform principles. the Project endeavors to identify patterns of teacher development, obstacles that must be overcome by developing teacher, and key issues that emerge in the development process. The Project also seeks evidence as to the effectiveness of particular teacher education practices in addressing particular problems of mathematics teacher education. The analysis of data is from a cognitive and a social perspective and focuses on both the individual and the collective development of the teachers involved. The Project employs a research methodology that incorporates whole-class constructivist teaching experiments and case studies of individual participants to study the development of the prospective and inservice teachers during and following a three-year instructional program. Central to the MTD research effort is unique, extensive, and state-of- the-art teacher development program designed to promote in-depth development as a context for inquiry.