In the arenas where the two world histories have taken shape, educators vigorously debate among themselves intellectual, pedagogical, and policy issues surrounding world history as a school subject. The people in each arena tend to share, despite internal disagreements, a common set of premises and assumptions for ordering the discussion of world history as a research and teaching endeavor. But in the two arenas the premises are quite different. Individual educators sometimes leave their own arena to visit the other one, but the two groups rarely hold joint meetings. In this article, the author examines the world history curriculum in U.S. schools in light of new developments in world history scholarship. (Contains 19 notes.)