Role congruity theory predicts that women will be less likely than men to emerge as leaders when expectations for the leader role are incongruent with gender stereotypes. A 2 × 2 × 3 design that crossed the sex of the dominant partner, mixed- and same-sex dyads, and masculine, feminine, and neutral tasks involved 120 dyads of unacquainted college students in which one partner scored higher in dominance. In same-sex partnerships, the dominant member consistently emerged as leader. In mixed-sex dyads, the gender typing of the task did not influence dominant male ascendance but it did affect women's. When the task was masculine-typed or neutral, less dominant men were more likely to emerge as the leader of the dyad, frequently being appointed by the dominant woman herself. Thus, even when women possess the agentic quality of dominance consistent with the leader role, the incongruence between masculinized task demands and gender stereotypes mitigate against women's leadership emergence.