We rely on a series of data sources. To assess the voting behaviour of MPs, we rely on a dataset of all votes having occured in the Swiss lower house (made available by the Schweizerische Parlamentsdienste, Bundeshaus, Bern). This dataset allows us to assess quite precisely the role that party pressure and electoral concerns play in the MPs' voting behaviour. Second, we conducted an (internet-based) survey to collect information on the MPs' political preferences, their attitudes towards party discipline, the way they deal with complex agenda-structures, their risk attitudes and their own ideal of political representation. Third, we used various existing data sources to yield information on the (average) preferences in the electoral districts and on MPs and their parties. These included: expert surveys on the political positions of the Swiss parties, other MPs' surveys such as smartovte, statistical information on Swiss constituencies (the cantons), official statistical information about the individual electoral results of the MPs. We combined these various data sources to a huge data pool which we use for an innovative investigation of the behaviour of Swiss MPs. Erhebungsverfahren: Online-Survey Erhebungseinheiten: All member of the federal assembly (Upper House: 46, Lower House: 200) Auswahlverfahren: census Anzahl Untersuchungseinheiten: planned: 246, realised: 160 (65%) Untersuchungsdesign: surveys realised during winter session 2006 and summer session 2007 Durchführung der Feldarbeit: project assistant