Manometric evaluation of pharyngeal contraction and upper esophageal sphincter relaxation was performed in a group of patients with Zenker's diverticulum using a specially designed low compliance manometric recording system. The results were compared with those in normal controls. In all cases, the upper esophageal sphincter showed complete relaxation during swallowing and no incoordination between pharyngeal contraction and upper esophageal sphincter relaxation could be demonstrated compared to time intervals found in the control group. Resting upper esophageal sphincter pressures were significantly lower in diverticulum patients than in controls. It is concluded that symptomatic patients with Zenker's diverticulum have normal pharyngeal-upper esophageal sphincter coordination, exhibit complete upper esophageal sphincter relaxation on swallowing, and have low resting upper esophageal sphincter pressures. These results seriously question the previous concept of abnormalities of pharyngeal-upper esophageal sphincter coordination in patients with Zenker's diverticulum.