This is study of the effects of obstructing the opening to the vomeronasal organ (VNO) on feed consumption, weight gain and social structure of 22 2-year-old Santa Gertrudis steers under experimental feedlot conditions. Obstructions were produced by either cautery or plugging of the duct that leads to the VNO. Feed intake and weight gain were similar in all 3 groups (control, cauterized and plugged) before, during and after the 4-week experiment. The pre-treatment social hierarchy, determined by conventional inter-individual aggression contests, was distinctly changed, and higher ranking pre-treatment steers generally lost rank and lower ranking steers gained rank. Treated steers (plugged and cauterized) often gained rank over controls. Thus, we are led to postulate that the VNO has a role in the aggressive behaviors that contribute to social hierarchy in the bovine. © 1984.