From 30 experiments on eight adult cows it was found that the peristaltic wave of esophageal contraction associated with the swallowing of saliva traveled down the esophagus at a velocity of approximately 42 cm/sec. During rumination, the marked drop in intrapleural pressure appeared to contribute the primary force for the regurgitation of ingesta into the thoracic esophagus. This aspiratory movement was then followed by an antiperistaltic wave of esophageal contraction which traveled at a velocity of approximately 107 cm/sec. Eructation was accompanied by an esophageal pressure wave of two components. The characteristics of the first component could be explained by the filling of the esophagus with gas driven by the intraruminal/intraesophageal pressure differential and dilation of the pharyngeal esophageal sphincter early in this process. Contributing to the intraruminal/intraesophageal pressure difference were rumen contraction, a small superimposed abdominal press component, and the negative pressure in the thoracic esophagus. The second component of the esophageal pressure wave accompanying eructation was recorded as an antiperistaltic wave of contraction traveling at a mean velocity of 227 cm/sec.