We have examined the hypothesis that isolated pyloric pressure waves occur in the absence of even low-amplitude antral contractions. Antropyloroduodenal motility was recorded in seven healthy adult volunteers. A sleeve/side-hole manometric assembly was positioned across the pylorus with the aid of measurements of transmucosal potential difference. A new sensor consisting of an elliptical wire transducer 2.5 cm long and 1.5 cm in transverse diameter was incorporated into the assembly above the sleeve. This sensor was designed to detect nonlumen-occluding antral contractions. Motility was studied for 45 min under each of three conditions: 1) fasting, 2) after ingestion of a 100-g beef burger, and 3) during and after a 15-min intraduodenal infusion of 25% dextrose at a rate of 4 ml/min. Overall, only 51% of antral transducer deflections were associated with a change in antral side-hole pressures. Eighty-nine percent of antral side-hole pressure waves were associated with an indication of antral wall motion. Of the pressure waves recorded by the sleeve classified as isolated pyloric pressure waves, none was associated with antral transducer deflection during fasting, 1.1% after intraduodenal dextrose, and 18% after the solid meal. Antral contractions were detected by the wall motion detector with greater sensitivity than antral side holes, possibly reflecting the occurrence of nonlumen-occluding antral contractions. With some exceptions during solid gastric emptying, manometrically defined isolated pyloric pressure waves appear to represent truly localized contraction.