This study is concerned with the political impact of the Supreme Court's decisions concerning state legislative apportionment. First, an attempt is made to describe the political environment in which they were made, with special reference to the existing bases of representation in the states and the political reaction to the decisions. Secondly, the study traces the major issues relating to judicial enforcement of the apportionment standards enunciated by the Supreme Court and the modification and development of those standards that followed the initial decisions. Finally, the extent to which reapportionment has been successfully enforced by the courts may suggest some tentative conclusions about the viability and utility of the equal population doctrine as a constitutional standard, as well as some of the possible political consequences of enforcement of that standard.