Today's historic level of women in national parliaments—while still far short of parity at 16%—owes much to the global spread of gender quotas. This process, in turn, owes much to the concept of “critical mass”: International organizations, transnational networks, party politicians, women's activists, and even ordinary citizens argue that women should constitute 30% of all political bodies, the magic number where female legislators are said to be able to make a difference. As the notion of critical mass has gained wide currency in the real world, however, many scholars have come to question its utility and relevance for analyzing women's legislative behavior. Indeed, as the number of studies grows, it is increasingly obvious that there is neither a single nor a universal relationship between the percentage of women elected to political office and the passage of legislation beneficial to women as a group: In some cases, women are able to work more effectively together as their numbers grow, but in others, women appear to make a difference—in fact, sometimes a greater difference—when they form a small minority of legislators, either because their increased numbers provoke a backlash among male legislators or because their increased numbers allow individual women to pursue other policy goals. These contradictions thus raise the question: Should feminists give up on critical mass? Or are there any compelling reasons—either theoretical or practical—for retaining the concept in debates on women's political representation?