BACKGROUND/AIMS: High-resolution manometry (HRM) is a new methodology that can be done at any position. The aim of this study was to determine whether the body position affects the esophageal manometric parameters. METHODS: Twenty nine subjects (15 males and 14 females, age: 53.1+/-13.2) were studied with a 36-channel HRM assembly. The subjects performed ten 5-mL water-swallows in the sitting position. At 15 minutes, the same study was done in the supine position. The basal mean LES pressure and the UES pressure, the mean wave amplitude, the velocity and the deglutitive relaxation were analyzed automatically using ManoViewTM. The Pressurization front velocity (PFV) and distal contractile integral (DCI) were manually calculated using the Smart Mouse tool in ManoViewTM. We used the Chicago classification1 for the diagnosis. RESULTS: The mean manometric parameters in the sitting and supine positions were the basal LES pressure (20.9+/-7.0 mmHg vs 22.4+/-8.3 mmHg, respectively, p=0.28), the basal UES pressure (51.0+/-30.2 mmHg vs 49.7+/-17.2 mmHg, respectively, p=0.11), the wave amplitude (64.7+/-29.0 mmHg vs 73.9+/-41.0 mmHg, respectively, p=0.19), velocity (5.4+/-4.5 cm/s vs 5.8+/-5.3 cm/s, respectively, p=0.91), the PFV (4.2+/-1.2 cm/sec vs 4.3+/-0.9, respectively, p=0.70), and the deglutitive relaxation (9.2+/-4.6 mmHg vs 11.2+/-4.3, respectively p=0.23). Only the DCI was significantly increased in the supine position (2625.6+/-1265.9 mmHg.s.cm vs 3426.4+/-1542.6 mmHg.s.cm, respectively, p<0.01). A different final diagnosis was noted in 7 subjects (24.1%) at each position. CONCLUSIONS: The patient position during HRM study may affect the esophageal motor parameters and the final diagnosis.