This paper examines changes between 1992 and 2010 in Japanese junior high school history textbooks' representations of imperial Japan's colonialism and aggression in Asia, using documentary study and interviews with actors in the textbook production process. Following a trend to increase textbook material on Japan's wartime aggression in the mid-1990s, after 2000 publishers approached this topic in contrasting ways, some expanding and some reducing their coverage, with dramatically varying results in terms of market share. Publishers' decisions on content were related to their market position and to changes in local textbook adoption procedures that have increased the decision-making power of appointed boards of education at the expense of teachers. Increased market share since 2000 is associated primarily with a progressive pedagogy in tune with recent curriculum reforms. The recent spotlight on textbook adoption has exposed weaknesses in the system, such as inadequate representation of the local community and insufficient guarantee of teachers' expert input in the adoption process. With the introduction of new textbook approval criteria requiring their conformity with the patriotic emphases of the revised Fundamental Law on Education of 2006, the content of future textbooks will clearly be strongly influenced by both approval and adoption processes. © 2012 Cambridge University Press.