BACKGROUND: Although, the current protocol for high resolution manometry (HRM) using the Chicago Classification is based on the supine posture, some practitioners prefer a sitting posture. Our aims were to establish normative esophageal pressure topography data for the sitting position and to determine the effect of applying those norms to Chicago Classification diagnoses. METHODS: Esophageal pressure topography studies including test swallows in both a supine and sitting position of 75 healthy volunteers and 120 patients were reviewed. Integrated relaxation pressure (IRP), distal contractile integral (DCI), contractile front velocity (CFV), and distal latency were measured and compared between postures. Normative ranges were established from the healthy volunteers and the effect of applying sitting normative values to the patients was analyzed. KEY RESULTS: Normative values of IRP, DCI, and CFV all decreased significantly in the sitting posture. Applying normative sitting metrics to patient studies [27% reduction in IRP (15 to 11 mmHg), 69% reduction in DCI (8000-2500 mmHg-s-cm)] reclassified 13/120 (11%) patients as having abnormal esophagogastric junction relaxation and 26/120 (22%) as hypercontractile. Three patients with an abnormal supine IRP normalized when sitting with elimination of a vascular artifact. CONCLUSIONS & INFERENCES: Clinical HRM studies should include both a supine and sitting position to minimize misdiagnoses attributable to anatomical factors. However, until outcome studies demonstrating the significance of isolated abnormalities of IRP or DCI in the sitting position are available, the Chicago Classification of esophageal motility disorders should continue to be based on supine swallows using normative data from the supine posture.