Abstract.  Although expert surveys have gained a prominent place in comparative studies of party positions on issues, their validity has been called into question. In this article, some of the validity concerns are evaluated in the context of the authors' own expert survey on national party positions vis-à-vis European integration. One goal of the article is to demonstrate that this expert survey produces valid measures of party positions. An equally important goal, however, is to suggest some methods that can help in assessing the quality of expert survey data. These methods, which are rooted in psychometric theory, are applicable in a variety of contexts and are easily implemented.