Various authors have argued that the behavior of voters as well as parties in most West European countries is structured mainly by an ideological `left-right' dimension. However, it remains unclear how the dimension labeled `left-right' by those studying party behavior relates to voters' perceptions of this dimension of conflict. This study assesses the extent to which Dutch voters' perceptions of parties' left-right positions reflect policy positions of parties determined by the contents of election programs. The research design is dynamic, allowing one to observe changes in party positions, as well as dynamic changes in the structure of a party system. The analyses show that the contents of party programs are strongly linked to voters' perceptions of parties' left-right positions, but that the strength of this linkage has decreased gradually since the late 1970s. Repercussions for political representation are discussed.