The present study is aimed at establishing the values of internal jugular vein (IJV) anterior-posterior and medial-lateral sizes in patients with hypovolemia. A total of 25 adult Intensive Care Unit patients with hypovolemia were studied. It was found that the anterior-posterior vein size in patients with hypovolemia was significantly less than medial-lateral size during inhalation and during exhalation as well (P < 0.05). Besides, the value of the anterior-posterior size (Dmin) <7 mm was recorded in 20 from 25 patients (80%). At the same time, the medial-lateral size (Dmin) <7 mm was recorded only in six patients (24%). In patients with hypovolemia, the medial-lateral diameter of IJV is more than its anterior-posterior diameter. These data might be useful for justifying the benefits of using lateral access for IJV catheterization under ultrasound imaging in patients with hypovolemia.