With funding from the National Science Foundation (NSF) in 1991-1996, and in 2000-2006, the Connected Mathematics Project (CMP) developed a complete mathematics curriculum for middle school teachers and students. CMP helps students and teachers develop understanding of important mathematical concepts, skills procedures, and ways of thinking and reasoning, in number, geometry, measurement, algebra, probability and statistics. CMP is based on research, and was field-tested in diverse sites across the country with approximately 45,000 students and 390 teachers. Each unit, in both 1991-1996 and 2000-2006 development periods, went through at least 3 cycles of field testing. A growing body of research and evaluation reports (2006 Evaluation Booklet, New Studies, CMP Literature Review 2010) indicates that CMP outperforms non-CMP curricula on tests of problem-solving ability, equals or outperforms non-CMP curricula on skills tests, and promotes long term retention.