Eighty-seven patients who had sonographic examinations at the Orange County Medical Center were studied retrospectively to evaluate the usefulness and reliability of this noninvasive technique, and sonographic results were compared with findings at operation or findings made using other diagnostic methods. With a variety of lesions, the overall accuracy of diagnosis by sonography was 85%. In the remaining 15% of studies, false-positive or false-negative results were observed. The accuracy varied with the organ involved, the greatest being renal and hepatic masses. Ultrasound, when used in addition to careful surgical assessment of the patient, was found to be most useful in the diagnosis and follow-up of abdominal problems in surgical patients.