After the introduction in Section 2, we very briefly sketch out current theoretical and empirical developments in the social sciences. In our view, they all point in the same direction: toward the acute and increasing need for multidisciplinary longitudinal data covering a wide range of living conditions and based on a multitude of variables from the social sciences for both theoretical investigation and the evaluation of policy measures. Cohort and panel studies are therefore called upon to become truly interdisciplinary tools. In Section 3, we describe the German Socio-Economic Panel Study (SOEP), in which we discuss recent improvements of that study which approach this ideal and point out existing shortcomings. Section 4 concludes with a discussion of potential future issues and developments for SOEP and other household panel studies.