Electoral gender quotas now exist in a majority of national legislatures worldwide. In general, quotas are followed by greater legislative attention to the interests and priorities of women as a group. Across cases, effects have been most pronounced on issues related to women's rights, public health, and poverty alleviation. Quotas can influence policy in two general ways: First, quotas may send cues to all officeholders, prompting broad changes in legislator behavior among both men and women. Second, quotas typically bring more women into legislatures, causing a shift in aggregate legislator preferences and increasing women's ability to collectively influence legislative decisions. Yet, the positive effects of quotas are not universal, and some research reveals instances in which quotas have led to limited policy changes or even to more gender-inegalitarian outcomes. I suggest several variables that may moderate the relationship between quota adoption and policy change, including underexplored dimensions of quota design.