In 1998, the American Museum of Natural History (AMNH) launched an ambitious effort to create on-line science courses for K-12 educators that would immerse them in exciting science topics and give them access to the Museum's scientific resources (scientists, research, expeditions, collections, and exhibitions). This project, called Seminars on Science, ultimately yielded 10 graduate-level courses on a range of topics. Inverness Research Associates studied the courses from their inception until 2006. Research revolved around these nine questions: (1) What is the quality and rigor of the science content? (2) What is the nature of the course-taking experience for teachers? (3) To what extent do teachers actually gain access to working scientists and AMNH resources? (4) How well organized and facilitated are the courses? (5) How do the courses benefit teachers as adult learners? (6) How do the courses benefit teachers in their role as educators? (7) To what extent and in what ways can teachers use what they learn in their own teaching? (8) How do teachers believe their students benefit? and (9) How do the courses appear to add value to districts' standards-based science initiatives and professional development programs? This report summarizes overall findings, using evidence drawn from surveys, interviews, teacher profiles, and independent expert reviews.