To compare the effect of Valsalva maneuver and 10 degrees Trendelenburg position on the right internal jugular vein (RIJV), we measured RIJV cross-sectional area using ultrasound imaging during these procedures. The study group consisted of 13 normal healthy volunteers (6 males, 7 females, aged 25-47) with no history of neck surgery or right internal jugular vein (RIJV) puncture. All ultrasound images were obtained at the level of the cricoid cartilage. The subjects were positioned supine, and the measurements were taken with the subjects supine, under Valsalva maneuver, and under 10 degrees Trendelenburg tilt position. The cross-sectional areas of the RIJV during Valsalva maneuver and 10 degrees Trendelenburg position compared to those with supine position were 314 +/- 162%, and 192 +/- 96%, respectively. We conclude that both procedures increase cross-sectional area of IRJV significantly and in this respect Valsalva maneuver is more effective than Trendelenburg position.