The diagnostic accuracy and the clinical impact of routine ultrasonography performed by 4 surgeons, were prospectively studied in 366 unselected patients admitted for suspected acute appendicitis. Clinical and sonographic findings on admission were correlated with laparotomy findings, pathological outcome and clinical as well as follow-up data. The overall sensitivity, specificity and accuracy of the clinical diagnosis of acute appendicitis were 55.3%, 94.6% and 84.2% respectively (positive predictive value (PPV) 75.8%, negative predictive value (NPV) 87.3%). Ultrasound enabled visualization of the disease in 67 of 85 (prevalence 23.3%) patients with a histologically confirmed acute appendicitis; false positive results were recorded in 7 cases (sensitivity 78.8%, specificity 97.5%, accuracy 93.1%, PPV 90.5%, NPV 93.8%). Ultrasound was particularly useful in patients presenting with equivocal or highly unsuspective signs of acute appendicitis: of 38 patients with an acute appendicitis in this group ultrasonography enabled to make the diagnosis in 26. The combined approach of clinical evaluation and routine ultrasonography markedly improved the diagnostic accuracy (sensitivity 85.9%, specificity 96.4%, accuracy 94%) and substantially reduced the negative laparotomy rate (7.9%) in patients with suspected acute appendicitis. It is concluded, that ultrasonographic evaluation of the patient with suspected acute appendicitis performed by surgeons is of great assistance in surgical practice.