Canadian and American research finds that organized labor's engagement with race, ethnicity, gender, and sexual orientation until recently has been largely exclusionist. The Canadian labor movement emerges as having been somewhat more responsive to equity issues, particularly gender and sexual orientation, and at an earlier stage than its U.S. counterpart. The American movement, however, did create limited room for African-American issues and unionization from early this century and now shows signs of broader engagement with diversity issues in general. The literature is strong in case studies pointing to exceptional situations involving minority militancy and union acceptance and in highlighting the role of activists inside and external to the labor movement. It suffers from a lack of large-scale analysis and comparison.Has organized labor been an ally or a foe for women and minority groups seeking equal opportunities and equitable treatment in the labor force and workplace? There is now a substantial body of literature focused on this question, and recent changes in union response to issues of diversity call out for a summary and assessment of this literature. This article considers scholarship on race, ethnicity, gender, and sexual orientation in Canada and the United States.