This paper first reviews a number of epistemological and methodological issues relating to the estimation of party policy positions, particularly in a comparative context, with special reference to the methodology of ‘expert surveys’. It is argued that expert surveys, as systematic summaries of the views of country specialists, have a particular role in assessing the content validity of other types of estimates of party policy positions. The paper moves on to analyze the positions of Japanese political parties in a comparative context, using results from a new 47-country expert survey. Attention is paid both to the substantive policy content of the left–right dimension in Japan, and to the locations of Japanese parties in policy spaces, relative to the locations of comparable parties in other political systems.