Abstract. We propose a measure of voter ideology which combines party manifesto data compiled by Budge, Robertson, Heari, Klingemann, and Volkens (1992) and updated by Volkens (1995), with election return data. Assuming the comparability and relevance of leftright ideology, we estimate the median voter position in 15 Western democracies throughout most of the postwar period. The plausibility of our assumptions, and therefore the validity of our measure, is supported by the results of several validity tests. With this new measure we are able to make crossnational comparisons of voter ideology among these countries as well as crosstime comparisons within individual countries. We discuss the potential application of our measure to various debates in political science.