A measuring unit combined with a perfused catheter has been developed for measurement of the pharyngo-oesophageal sphincter pressure. The system is able to register pressure measurements using either intermittent or continuous withdrawal of the catheter, at the same flow rate (0.5 ml/min). Repeated measurements of pharyngo-oesophageal sphincter pressure have been made on eight healthy volunteers. No differences were found in the sphincter pressures measured by the continuous and the intermittent withdrawal techniques (p greater than 0.10); the coefficient of variation was 0.18 for both techniques. The pharyngo-oesophageal sphincter pressure was measured during infusion of 0.1 N HCl (5 ml/min) 5 cm proximally to the gastro-oesophageal sphincter. There was an increase in the pharyngo-oesophageal sphincter pressure after 1 min of infusion (p less than 0.05). Measurements after 5 min and 10 min were no different from the initial value; thus a fall was observed between the first and the fifth minute (p less than 0.05). The observed rise in sphincter pressure may be explained as a response acting to prevent gastro-oesophageal reflux from entering the pharynx.