RBS Currents, Volume 5, Issue 2 RBS' interest in lesson study grew out of collaborative work with the U.S. Department of Education to disseminate data from the Third International Mathematics and Science Study (TIMSS). Delving deeper into TIMSS and related research, we met two key individualsHarold Stevenson and Catherine Lewiswithout whom our journey beyond TIMSS would not have led to lesson study. Our understanding evolved with the help of Clea Fernandez and Makoto Yoshida, who provided opportunities to observe lessons at the Greenwich Japanese School. But it has been primarily through our four-year relationship with Lynn Liptak and the staff at Paterson School 2 that we have learned up close about the challenges and rewards of "sticking with it" while continually refining our understanding of what lesson study offers.