Quotas have become an important mechanism through which women today are entering legislatures worldwide. This study shows that the introduction of quotas has helped overcome constraints on women's representation posed by economic underdevelopment, cultural influences, and even electoral systems. This study also demonstrates that the introduction of quotas offers the most explanatory power for women's representation today, together with electoral systems that allow for greater candidate turnover (i.e., party-list proportional representation systems). The majority of studies explaining women's legislative representation prior to 2000 focused on electoral systems, cultural considerations, and the strength of leftist political parties. Since the mid-1990s, however, an increasing number of countries have introduced gender quotas, which this article incorporates into older models in cross-national multivariate analysis.