Power is at the core of feminist theories of sexual harassment, though it has rarely been measured directly in terms of workplace authority. While popular characterizations portray male supervisors harassing female subordinates, power-threat theories suggest that women in authority may be more frequent targets. This article analyzes longitudinal survey data and qualitative interviews from the Youth Development Study (YDS) to test this idea and to delineate why and how supervisory authority, gender non-conformity, and workplace sex ratios affect harassment. Relative to non-supervisors, female supervisors are more likely to report harassing behaviors and to define their experiences as sexual harassment. Sexual harassment can serve as an "equalizer" against women in power, motivated more by control and domination than by sexual desire. The interviews point to social isolation as a mechanism linking harassment to gender non-conformity and women's authority, particularly in male-dominated work settings.