Although the ultrasonography has been regarded as a important procedure in the diagnosis of intra-abdominal abscess, there were relatively few papers concerning the ultrasonographic findings of periappendiceal abscess. Nineteen cases of surgically proven periappendiceal abscess caused by perforated appendicitis were studies by ultrasonography at the Kyung Hee University Hospital during last 34 months. The results were as follows : 1. Diagnostic accuracy of the real-time ultrasonography was 94.7% (18/19). There were only one false positive and one false negative. 2. The location of abscesses were ; periappendiceal 68.4% (13/19), pelvic 21.0% (4/19), subhepatic 5.3% (1/19) and subphrenic 5.3% (1/19) in order of frequency. 3. Variable echo-patterns of abscesses were encountered. But irregular, thick walled, posteriorly rein-forcing, echo-free or mixed echo-patterns were most common.