This article follows a revised political opportunity approach to argue that mobilization of underprivileged groups is constrained by the political opportunity structures provided by the institutional context of the country in which they act. Contrary to traditional opportunity theories, it is suggested that their mobilization also depends on a set of opportunities specific to the political or issue field most directly addressed by their claims. I propose to look for these specific opportunities in the institutional approaches to unemployment. I further maintain that such opportunities stem largely from the ways in which a given political or issue field is collectively defined. I apply a theoretical framework stressing both general and specific opportunities as well as the discursive context of claim making to original data on claim making in the unemployment political field in six European countries for the 1995-2002 period. The findings provide some support for the proposed theoretical framework, but also point to its shortcomings, especially in the lack of attention to economic factors.