The Diversity in Mathematics Education Center for Learning and Teaching (DiME) is a consortium of three universities and three school districts which focuses on issues of equity in mathematics education. Consortium partners are the University of Wisconsin-Madison, the University of California at Los Angeles, the University of California at Berkeley, the Madison Metropolitan School District, a local district of the Los Angeles School District, the California Mathematics Project, and the Berkeley Unified School District. During the first four years of DiME, we have developed and instantiated a three-campus center for preparing mathematics education leaders to address issues of equity in the teaching and learning of mathematics. We have developed new graduate courses and cross-campus seminars, implemented professional development programs grounded in teachers’ practice and focusing on equity, and initiated a program of research focused on equity in mathematics education. We have made a great deal of progress in developing a community of scholars poised to address some of the most critical problems facing mathematics education. We see DiME’s research and professional development efforts as being deeply intertwined, and we have engaged in sustained professional development at each of the sites focusing on equity in mathematics teaching and learning.