During a 12-month period high-resolution, real-time ultrasonography (US) with graded compression was performed on 268 consecutive patients with clinically suspected acute appendicitis and its complications. US visualization of a fluid-filled, non-compressed appendix or a decompressed, thick-walled appendix was the primary criterion for a diagnosis of acute appendicitis. The sonographic ficdings were correlated with surgical-pathologic outcome in 92 cases and with the findings of clinical follow-ups in the remainder, US was found to be accurate in the diagnosis of acute appendicitis and its complication with a sensitivity of 93.3%, a specificity of 98.9% and an accuracy of 9.7%. The predictive value of a positive test was 97.7%, that of a negative test was 96.7% There were two false-paositive examinations in patients with a thick-walled appendix or periapperdiceal abscess, which were six false-negative examinations in patients with a sonographically no-visible appendix, which were confirmed surgically as acute appendicitis (n=5) and perforated appendicitis (n=1). Our results show that high-resolution, real-time US is an accureate imaging modality in the diagnosis of acute appendicitis and the evaluation of its complications.