This research investigated gender differences and longitudinal effects in dominance hierarchy organization based on verbal interruptions in same-sex small discussion groups. Participants (58 women, 58 men; average age = 37.5) met twice in the same groups to debate for 45 minutes. The use of a newly developed coding system allowed assessing the winner and loser of an interruption and identification of dominant individuals. On the basis of dyadic dominance matrices, the degree of linearity and temporal stability were computed. Results showed that women were less hierarchically organized than men only at the very beginning of the interaction. With time, men decreased and women first increased and then decreased in hierarchical organization. Rank orders in all-male as well as all-female groups were unstable across time. Three different models describing the possible nature of dominance hierarchies are presented, and results are discussed and integrated in reference to them.