BACKGROUND: The purpose of this study was to evaluate the anatomies of the internal jugular vein (IJV) and of the carotid artery (CA) using two-dimensional ultrasound in Koreans. METHODS: Thirty-five healthy people, who had never undergone IJV cannulation, underwent IJV and CA imaging. Vessels in the neck were imaged with a 7.5-MHz transducer, perpendicular to the spinal axis. The lateral diameter and cross-sectional area (CSA) of IJV, and overlap diameter, and neck circumference were measured. Thereafter, percent (%) overlap and safe zone were calculated. RESULTS: The mean right IJV size was measured as lateral diameter, 1.42 cm, and CSA, 1.0 cm2, and was greater than that of left IJV (lateral diameter, 16.5% +/- 23.2%; CSA, 22.4% +/- 36.3%). CSA of IJV increased according to body mass index (BMI), but did not for neck circumference and body weight. As neck circumference and body weight increased, percent overlap decreased and the IJV safe zone increased. However, percent overlap and safe zone were not significantly different for right and left vessels. In a majority of subjects, the IJV was located anterolaterally (42.9%) or laterally (51.4%) to the CA by ultrasound imaging. 11.4% of right IJVs and 15.4% of left IJVs observed unusually microvessels (< 0.5 cm2). CONCLUSIONS: In Koreans, right IJVs were larger than left IJVs, and BMI was best correlated with IJV size. Koreans have a normal anatomical relationship between IJV and CA, however microvessels are relatively frequent.