A prospective ultrasonic study of the right lower abdominal quadrant was performed in 46 patients prior to appendicectomy. Ultrasonography revealed an inflamed appendix in 24 out of 29 patients with appendicitis and excluded its presence in 16 out of 17 patients without appendicitis. The ultrasonic pattern of the inflamed appendices appeared as echo-poor/echo-free lesions with lack of movement. In six of seven patients with perforated appendices, ultrasonography revealed free intra-abdominal fluid in addition to bowel disease. The possible value of abdominal ultrasound in patients with suspected acute appendicitis is discussed.