More and more countries are adopting quotas to increase group-based equality in the boardroom and the political sphere. Nevertheless, affirmative action in general and quotas in particular remain a highly controversial subjecteliciting negative reactions from privileged groups, while support among minority and lower-status groups is generally higher. Focusing on gender, we take a broad approach to the topic and discuss (a) the effects of quotas and affirmative action on the under-representation of minority groups and on perceptions of their competence, (b) the effects of quotas and affirmative action on organisational performance, and (c) predictors of attitudes towards affirmative action and quotas. We conclude that the benefits of quotas outweigh their costs and that they are an effective way of tackling group-based inequality. We also discuss strategies that can be used to elicit more support among those groups that are particularly critical of quotas.