PURPOSE: We wanted to evaluate the usefulness of the inner hypoechoic band in pediatric appendices as an ultrasonographic criterion to exclude or confirm acute appendicitis. MATERIALS AND METHODS: Among the 169 consecutive children with right lower abdominal pain, the 149 appendices depicted on US were prospectively evaluated for an inner hypoechoic band in the appendiceal walls. The sensitivity, specificity, positive and negative predictive values and accuracy were assessed for loss of the inner hypoechoic band as a diagnostic criterion for acute appendicitis. RESULTS: The appendices in 12 (25%) patients with acute appendicitis show entire inner hypoechoic bands and those in 36 patients (75%) did not. The appendices in 97 (96%) patients without acute appendicitis showed entire inner hypoechoic bands, and those in 4 (4%) did not. The loss of inner hypoechoic band confirmed acute appendicitis with a sensitivity of 75%, a specificity of 96%, positive and negative predictive values of 89% and 90%, respectively, and an accuracy of 89%. The thickness of the inner hypoechoic band in patients without appendicitis was significantly higher than that in patients with appendicitis (p = 0.03). CONCLUSION: The visualization of entire thickened inner hypoechoic band in the appendiceal wall helps to rule out acute appendicitis. However, the loss of the inner hypoechoic band is suggestive of acute appendicitis.