How would instruction and student learning improve if educators made the time to really understand and practice a new curriculum before implementing it in classrooms with students? In Orange County, California, educators are finding out by testing an approach of preimplementation professional learning for a full year before applying a new curriculum. Along with two other conditions -- setting an instructional vision and preparing for a robust adoption process -- the authors believe that investing in curriculum-based professional learning from the very beginning -- in the phase before curriculum implementation -- will allow districts to reap benefits for years to come.