Lesson study is the major form of professional development in Japan and has attracted attention in the United States in recent years. Lesson study currently conducted in Japan varies in terms of length, structure, and scale. District-level mathematics lesson study gathers teachers from different schools who share an interest in teaching the subject, and the discussion can focus more on particular aspects of teaching mathematics or content issues than that of in-school lesson study. The results of the survey indicate that lesson study provides opportunities for better communication among teachers, researchers, and administrators by presenting concrete classroom teaching examples surrounding particular educational ideas and/or issues, thus minimizing the gap among theory, research, and practice. Implications to U.S. schools are discussed. (Author)