This paper investigates the evolution of the interest groups system in Denmark and Switzerland. Denmark is an emblematic example of social corporatism, while Switzerland is a paradigmatic case of liberal corporatism. However, neo-corporatist arrangements are put under strong and cumulative pressures in both countries, for instance through Europeanization, party polarization, mediatization, revalorization of the Parliament, "pluralization" of interest representation, etc. As similar external factors have impacted the two different interest groups systems, one might wonder if the transformation of corporatism in Denmark and Switzerland leads towards a new and common form of interest group system. The paper analyze the presence of interest groups, in the two major venues of the legislative process (administrative and parliamentary venues), and ask if we observe a decline in the role of corporatist interest groups. Can we observe a trend toward “parliamentary corporatism”, marked by increasing involvement of corporatist actors in the parliamentary venue and declining presence in the traditional corporatist administrative venue? To address these research questions, a longitudinal study will compare which interest groups had privileged access in the decade 1975-1985 versus in 2010. In the administrative venue, we look at seats in public committees. In the parliamentary venue, we measure another indicator of privileged access, namely the number of interest groups to which an MP is affiliated (as simple member, board member or paid official) in 1985 and in 2010. The proposed combination of longitudinal, cross-sectional and cross-country comparisons aims at systematically mapping and comparing two national interest groups systems. This approach is innovative as comparative studies are not so numerous (page 3 and 4 of workshop call). Last but not least, the proposed paper lies at the crossroad of the literature on national interest groups system, and the neo-corporatist theory as developed by Schmitter and Streeck.