To understand the mechanisms for introducing urine or vaginal secretions into the vomeronasal organ, we used 16 mm cinematography and a freeze frame/slow motion technique to analyze the mouth and tongue movements of Brahman bulls while they examined the vulvas of restrained, estrogen-primed cows. Prior to flehmen, the mouth slowly opened, the curled tip of the tongue compressed the hard palate and the body of the tongue protruded from the mouth. The tongue maintained this form and moved forward. Once the tip of the tongue reached the incisive papilla, the body of the tongue retracted and the tip of the tongue relaxed. This tongue compression stroke (TCS) of the hard palate occurred 2 to 6 times, lasting 1 4 to 1 2 sec/stroke. Pressure changes in the vomeronasal organ are assumed to occur during and following TCSs, resulting in aspiration of any liquid in the incisive pit into the incisive and vomeronasal ducts. Such aspiration probably does not occur during flehmen because the tongue is relaxed and on the floor of the mouth.