BACKGROUND/AIMS: We used high-resolution impedance manometry (HRIM) to determine the length of breaks on the isobaric contour which would predict incomplete bolus clearance in patients in the sitting position. METHODS: In total, 651 swallows in 71 patients with esophageal symptoms were studied using a solid-state HRIM system in the sitting position. Each swallow was classified as complete or incomplete bolus clearance by impedance criteria and peristaltic integrity was evaluated using 20- and 30-mmHg pressure topography isobaric contours. Correlations between the lengths of the breaks for 20- and 30-mmHg were analyzed. RESULTS: Complete bolus clearance was observed in 83.3% (542/651) of swallows. Breaks of 3 and 7 cm or less were associated with a bolus clearance of 96.8% on the 20-mmHg and 94.7% on the 30-mmHg isobaric contour, respectively (P < 0.001). The areas under the ROC curves for the 20 and 30 mmHg isobaric contours were 0.900 and 0.950, respectively. The sensitivity and specificity for complete bolus clearance were 75.6% and 89.3% for breaks 3 cm or less on the 20-mmHg isobaric contour and 87.9% and 78.7% for breaks 7 cm or less on the 30-mmHg contour (P < 0.001). CONCLUSIONS: Breaks of < 3 cm in the 20-mmHg isobaric contour or < 7 cm in the 30-mmHg isobaric contour were associated with com -plete bolus clearance. The threshold for breaks in the sitting position was greater than previous reports using the supine position and longer breaks predicted incomplete bolus clearance.