The 'patterned interaction' of political parties, to use Sartori's memorable definition of a party system, has long been the subject of scholarly inquiry. Yet, the ways in which the institutions of gender are embedded within the functioning of party systems appears to have largely escaped scrutiny so far. To date, scholarly attention has focused primarily on one aspect of this process: the potential contagion effects of shifts in women's descriptive and substantive representation within a given party system. The paper proposes a theoretical framework for analysing how gendered institutions (norms, rules) are first embedded into and subsequently reproduced during the formation and consolidation of the post-communist party systems of Central and Eastern Europe. The focus is on quotas for women's representation and reproductive rights respectively.